Mercurial > octave-nkf
annotate doc/interpreter/tips.txi @ 10846:a4f482e66b65
Grammarcheck more of the documentation.
Use @noindent macro appropriately.
Limit line length to 80 characters.
| author | Rik <octave@nomad.inbox5.com> |
|---|---|
| date | Sun, 01 Aug 2010 20:22:17 -0700 |
| parents | 322f43e0e170 |
| children | fd0a3ac60b0e |
| rev | line source |
|---|---|
| 8920 | 1 @c Copyright (C) 1996, 1997, 1999, 2002, 2004, 2005, 2007, 2008, |
| 2 @c 2009 John W. Eaton | |
| 7018 | 3 @c |
| 4 @c This file is part of Octave. | |
| 5 @c | |
| 6 @c Octave is free software; you can redistribute it and/or modify it | |
| 7 @c under the terms of the GNU General Public License as published by the | |
| 8 @c Free Software Foundation; either version 3 of the License, or (at | |
| 9 @c your option) any later version. | |
| 10 @c | |
| 11 @c Octave is distributed in the hope that it will be useful, but WITHOUT | |
| 12 @c ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 @c FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 @c for more details. | |
| 15 @c | |
| 16 @c You should have received a copy of the GNU General Public License | |
| 17 @c along with Octave; see the file COPYING. If not, see | |
| 18 @c <http://www.gnu.org/licenses/>. | |
| 3294 | 19 |
|
9032
349616d9c38e
Cleanup top-level documentation menu in octave.texi
Rik <rdrider0-list@yahoo.com>
parents:
8920
diff
changeset
|
20 @node Tips and Standards |
| 3294 | 21 @appendix Tips and Standards |
| 22 @cindex tips | |
| 23 @cindex standards of coding style | |
| 24 @cindex coding standards | |
| 25 | |
| 26 This chapter describes no additional features of Octave. Instead it | |
| 27 gives advice on making effective use of the features described in the | |
| 28 previous chapters. | |
| 29 | |
| 30 @menu | |
| 31 * Style Tips:: Writing clean and robust programs. | |
| 32 * Coding Tips:: Making code run faster. | |
| 33 * Comment Tips:: Conventions for writing comments. | |
| 34 * Function Headers:: Standard headers for functions. | |
| 6574 | 35 * Documentation Tips:: Writing readable documentation strings. |
| 3294 | 36 @end menu |
| 37 | |
| 4167 | 38 @node Style Tips |
| 3294 | 39 @section Writing Clean Octave Programs |
| 40 | |
| 41 Here are some tips for avoiding common errors in writing Octave code | |
| 42 intended for widespread use: | |
| 43 | |
| 44 @itemize @bullet | |
| 45 @item | |
| 46 Since all global variables share the same name space, and all functions | |
| 47 share another name space, you should choose a short word to distinguish | |
| 48 your program from other Octave programs. Then take care to begin the | |
| 49 names of all global variables, constants, and functions with the chosen | |
| 50 prefix. This helps avoid name conflicts. | |
| 51 | |
| 52 If you write a function that you think ought to be added to Octave under | |
| 53 a certain name, such as @code{fiddle_matrix}, don't call it by that name | |
| 54 in your program. Call it @code{mylib_fiddle_matrix} in your program, | |
| 5041 | 55 and send mail to @email{maintainers@@octave.org} suggesting that it |
| 3294 | 56 be added to Octave. If and when it is, the name can be changed easily |
| 57 enough. | |
| 58 | |
| 59 If one prefix is insufficient, your package may use two or three | |
| 60 alternative common prefixes, so long as they make sense. | |
| 61 | |
| 62 Separate the prefix from the rest of the symbol name with an underscore | |
| 63 @samp{_}. This will be consistent with Octave itself and with most | |
| 64 Octave programs. | |
| 65 | |
| 66 @item | |
| 67 When you encounter an error condition, call the function @code{error} | |
| 68 (or @code{usage}). The @code{error} and @code{usage} functions do not | |
| 69 return. | |
| 70 @xref{Errors}. | |
| 71 | |
| 72 @item | |
| 73 Please put a copyright notice on the file if you give copies to anyone. | |
| 74 Use the same lines that appear at the top of the function files | |
| 75 distributed with Octave. If you have not signed papers to assign the | |
| 76 copyright to anyone else, then place your name in the copyright notice. | |
| 77 @end itemize | |
| 78 | |
| 4167 | 79 @node Coding Tips |
| 3294 | 80 @section Tips for Making Code Run Faster. |
| 81 @cindex execution speed | |
| 82 @cindex speedups | |
| 83 | |
| 84 Here are some ways of improving the execution speed of Octave programs. | |
| 85 | |
| 86 @itemize @bullet | |
| 87 @item | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
88 Vectorize loops. For instance, rather than |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
89 |
| 9356 | 90 @example |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
91 @group |
| 9356 | 92 for i = 1:n-1 |
| 93 a(i) = b(i+1) - b(i); | |
| 94 endfor | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
95 @end group |
| 9356 | 96 @end example |
| 97 | |
|
10846
a4f482e66b65
Grammarcheck more of the documentation.
Rik <octave@nomad.inbox5.com>
parents:
10828
diff
changeset
|
98 @noindent |
| 9356 | 99 write |
| 100 | |
| 101 @example | |
| 102 a = b(2:n) - b(1:n-1); | |
| 103 @end example | |
| 104 | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
105 This is especially important for loops with "cheap" bodies. Often it suffices |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
106 to vectorize just the innermost loop to get acceptable performance. A general |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
107 rule of thumb is that the "order" of the vectorized body should be greater or |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
108 equal to the "order" of the enclosing loop. |
| 9356 | 109 |
| 110 @item | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
111 Use built-in and library functions if possible. Built-in and compiled functions |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
112 are very fast. Even with a m-file library function, chances are good that it is |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
113 already optimized, or will be optimized more in a future release. |
| 9356 | 114 |
| 10812 | 115 For instance, even better than |
| 116 | |
| 117 @example | |
| 118 a = b(2:n) - b(1:n-1); | |
| 119 @end example | |
| 120 | |
|
10846
a4f482e66b65
Grammarcheck more of the documentation.
Rik <octave@nomad.inbox5.com>
parents:
10828
diff
changeset
|
121 @noindent |
| 10812 | 122 is |
| 123 | |
| 124 @example | |
| 125 a = diff (b); | |
| 126 @end example | |
| 127 | |
| 128 | |
| 9356 | 129 @item |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
130 Avoid computing costly intermediate results multiple times. Octave currently |
| 9356 | 131 does not eliminate common subexpressions. |
| 9486 | 132 Also, certain internal computation results are cached for variables. |
| 133 For instance, if a matrix variable is used multiple times as an index, | |
| 134 checking the indices (and internal conversion to integers) is only done once. | |
| 3294 | 135 |
| 136 @item | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
137 Be aware of lazy copies (copy-on-write). When a copy of an object |
|
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
138 is created, the data is not immediately copied, but rather shared. The actual |
|
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
139 copying is postponed until the copied data needs to be modified. For example: |
| 9356 | 140 |
| 141 @example | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
142 @group |
| 9356 | 143 a = zeros (1000); # create a 1000x1000 matrix |
| 144 b = a; # no copying done here | |
| 145 b(1) = 1; # copying done here | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
146 @end group |
| 9356 | 147 @end example |
| 148 | |
| 149 Lazy copying applies to whole Octave objects such as matrices, cells, struct, | |
| 150 and also individual cell or struct elements (not array elements). | |
| 151 | |
| 152 Additionally, index expressions also use lazy copying when Octave can determine | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
153 that the indexed portion is contiguous in memory. For example: |
| 9356 | 154 |
| 155 @example | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
156 @group |
| 9356 | 157 a = zeros (1000); # create a 1000x1000 matrix |
| 158 b = a(:,10:100); # no copying done here | |
| 159 b = a(10:100,:); # copying done here | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
160 @end group |
| 9356 | 161 @end example |
| 162 | |
| 163 This applies to arrays (matrices), cell arrays, and structs indexed using (). | |
| 164 Index expressions generating cs-lists can also benefit of shallow copying | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
165 in some cases. In particular, when @var{a} is a struct array, expressions like |
| 9356 | 166 @code{@{a.x@}, @{a(:,2).x@}} will use lazy copying, so that data can be shared |
| 167 between a struct array and a cell array. | |
| 168 | |
| 169 Most indexing expressions do not live longer than their `parent' objects. | |
| 170 In rare cases, however, a lazily copied slice outlasts its parent, in which | |
| 171 case it becomes orphaned, still occupying unnecessarily more memory than needed. | |
| 172 To provide a remedy working in most real cases, | |
| 173 Octave checks for orphaned lazy slices at certain situations, when a value | |
| 174 is stored into a "permanent" location, such as a named variable or cell or | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
175 struct element, and possibly economizes them. For example: |
| 9356 | 176 |
| 177 @example | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
178 @group |
| 9356 | 179 a = zeros (1000); # create a 1000x1000 matrix |
| 180 b = a(:,10:100); # lazy slice | |
| 181 a = []; # the original a array is still allocated | |
| 182 c@{1@} = b; # b is reallocated at this point | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
183 @end group |
| 9356 | 184 @end example |
| 3294 | 185 |
| 186 @item | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
187 Avoid deep recursion. Function calls to m-file functions carry a relatively |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
188 significant overhead, so rewriting a recursion as a loop often helps. Also, |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
189 note that the maximum level of recursion is limited. |
| 9356 | 190 |
| 191 @item | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
192 Avoid resizing matrices unnecessarily. When building a single result |
| 3294 | 193 matrix from a series of calculations, set the size of the result matrix |
| 194 first, then insert values into it. Write | |
| 195 | |
| 196 @example | |
| 197 @group | |
| 198 result = zeros (big_n, big_m) | |
| 199 for i = over:and_over | |
| 200 r1 = @dots{} | |
| 201 r2 = @dots{} | |
| 202 result (r1, r2) = new_value (); | |
| 203 endfor | |
| 204 @end group | |
| 205 @end example | |
| 206 | |
| 207 @noindent | |
| 208 instead of | |
| 209 | |
| 210 @example | |
| 211 @group | |
| 212 result = []; | |
| 213 for i = ever:and_ever | |
| 214 result = [ result, new_value() ]; | |
| 215 endfor | |
| 216 @end group | |
| 217 @end example | |
| 218 | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
219 Sometimes the number of items can't be computed in advance, and stack-like |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
220 operations are needed. When elements are being repeatedly inserted at/removed |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
221 from the end of an array, Octave detects it as stack usage and attempts to use a |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
222 smarter memory management strategy pre-allocating the array in bigger chunks. |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
223 Likewise works for cell and struct arrays. |
| 9356 | 224 |
| 225 @example | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
226 @group |
| 9356 | 227 a = []; |
| 228 while (condition) | |
| 229 @dots{} | |
| 230 a(end+1) = value; # "push" operation | |
| 231 @dots{} | |
| 232 a(end) = []; # "pop" operation | |
| 233 @dots{} | |
| 234 endwhile | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
235 @end group |
| 9356 | 236 @end example |
| 237 | |
| 3294 | 238 @item |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
239 Use @code{cellfun} intelligently. The @code{cellfun} function is a useful tool |
|
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
240 for avoiding loops. @xref{Processing Data in Cell Arrays}. |
| 10284 | 241 @code{cellfun} is often used with anonymous function handles; however, calling |
| 9356 | 242 an anonymous function involves an overhead quite comparable to the overhead |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
243 of an m-file function. Passing a handle to a built-in function is faster, |
|
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
244 because the interpreter is not involved in the internal loop. For example: |
| 9356 | 245 |
| 246 @example | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
247 @group |
| 9356 | 248 a = @{@dots{}@} |
| 249 v = cellfun (@@(x) det(x), a); # compute determinants | |
| 250 v = cellfun (@@det, a); # faster | |
|
9758
09da0bd91412
Periodic grammar check of Octave documentation files to ensure common format
Rik <rdrider0-list@yahoo.com>
parents:
9486
diff
changeset
|
251 @end group |
| 9356 | 252 @end example |
| 253 | |
| 254 @item | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
255 Octave includes a number of other functions that can replace common types of |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
256 loops, including @code{bsxfun}, @code{arrayfun}, @code{structfun}, |
|
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
257 @code{accumarray}. These functions can take an arbitrary function as a handle. |
| 10812 | 258 Be sure to get familiar with them if you want to become an Octave expert. |
| 10284 | 259 |
| 260 @item | |
| 9356 | 261 Avoid calling @code{eval} or @code{feval} excessively, because |
| 3294 | 262 they require Octave to parse input or look up the name of a function in |
| 263 the symbol table. | |
| 264 | |
| 265 If you are using @code{eval} as an exception handling mechanism and not | |
| 266 because you need to execute some arbitrary text, use the @code{try} | |
|
9038
fca0dc2fb042
Cleanup documentation files stmt.texi and func.texi
Rik <rdrider0-list@yahoo.com>
parents:
9032
diff
changeset
|
267 statement instead. @xref{The @code{try} Statement}. |
| 3294 | 268 |
| 269 @item | |
| 270 If you are calling lots of functions but none of them will need to | |
| 271 change during your run, set the variable | |
| 272 @code{ignore_function_time_stamp} to @code{"all"} so that Octave doesn't | |
| 273 waste a lot of time checking to see if you have updated your function | |
| 274 files. | |
| 275 @end itemize | |
| 276 | |
| 4167 | 277 @node Comment Tips |
| 3294 | 278 @section Tips on Writing Comments |
| 279 | |
| 280 Here are the conventions to follow when writing comments. | |
| 281 | |
| 282 @table @samp | |
| 283 @item # | |
| 284 Comments that start with a single sharp-sign, @samp{#}, should all be | |
| 285 aligned to the same column on the right of the source code. Such | |
| 286 comments usually explain how the code on the same line does its job. In | |
| 287 the Emacs mode for Octave, the @kbd{M-;} (@code{indent-for-comment}) | |
| 288 command automatically inserts such a @samp{#} in the right place, or | |
| 289 aligns such a comment if it is already present. | |
| 290 | |
| 291 @item ## | |
| 7345 | 292 Comments that start with a double sharp-sign, @samp{##}, should be aligned to |
| 3294 | 293 the same level of indentation as the code. Such comments usually |
| 294 describe the purpose of the following lines or the state of the program | |
| 295 at that point. | |
| 296 @end table | |
| 297 | |
| 298 @noindent | |
| 299 The indentation commands of the Octave mode in Emacs, such as @kbd{M-;} | |
| 300 (@code{indent-for-comment}) and @kbd{TAB} (@code{octave-indent-line}) | |
| 301 automatically indent comments according to these conventions, | |
| 302 depending on the number of semicolons. @xref{Comments,, | |
| 303 Manipulating Comments, emacs, The GNU Emacs Manual}. | |
| 304 | |
| 4167 | 305 @node Function Headers |
| 3294 | 306 @section Conventional Headers for Octave Functions |
| 307 @cindex header comments | |
| 308 | |
| 309 Octave has conventions for using special comments in function files | |
| 310 to give information such as who wrote them. This section explains these | |
| 311 conventions. | |
| 312 | |
| 313 The top of the file should contain a copyright notice, followed by a | |
| 314 block of comments that can be used as the help text for the function. | |
| 315 Here is an example: | |
| 316 | |
| 317 @example | |
| 6778 | 318 ## Copyright (C) 1996, 1997, 2007 John W. Eaton |
| 3294 | 319 ## |
| 320 ## This file is part of Octave. | |
| 321 ## | |
| 322 ## Octave is free software; you can redistribute it and/or | |
| 323 ## modify it under the terms of the GNU General Public | |
| 324 ## License as published by the Free Software Foundation; | |
| 7081 | 325 ## either version 3 of the License, or (at your option) any |
| 326 ## later version. | |
| 3294 | 327 ## |
| 328 ## Octave is distributed in the hope that it will be useful, | |
| 329 ## but WITHOUT ANY WARRANTY; without even the implied | |
| 330 ## warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR | |
| 331 ## PURPOSE. See the GNU General Public License for more | |
| 332 ## details. | |
| 333 ## | |
| 334 ## You should have received a copy of the GNU General Public | |
| 335 ## License along with Octave; see the file COPYING. If not, | |
| 7016 | 336 ## see <http://www.gnu.org/licenses/>. |
| 3294 | 337 |
| 338 ## usage: [IN, OUT, PID] = popen2 (COMMAND, ARGS) | |
| 339 ## | |
| 340 ## Start a subprocess with two-way communication. COMMAND | |
| 341 ## specifies the name of the command to start. ARGS is an | |
| 342 ## array of strings containing options for COMMAND. IN and | |
| 343 ## OUT are the file ids of the input and streams for the | |
| 344 ## subprocess, and PID is the process id of the subprocess, | |
| 345 ## or -1 if COMMAND could not be executed. | |
| 346 ## | |
| 347 ## Example: | |
| 348 ## | |
| 349 ## [in, out, pid] = popen2 ("sort", "-nr"); | |
| 350 ## fputs (in, "these\nare\nsome\nstrings\n"); | |
| 351 ## fclose (in); | |
|
7768
a2d9f325b65a
Use isschar instead of deprecated isstr
Rafael Laboissiere <rafael@debian.org>
parents:
7345
diff
changeset
|
352 ## while (ischar (s = fgets (out))) |
| 3294 | 353 ## fputs (stdout, s); |
| 354 ## endwhile | |
| 355 ## fclose (out); | |
| 356 @end example | |
| 357 | |
| 358 Octave uses the first block of comments in a function file that do not | |
| 359 appear to be a copyright notice as the help text for the file. For | |
| 360 Octave to recognize the first comment block as a copyright notice, it | |
| 6530 | 361 must start with the word `Copyright' after stripping the leading |
| 362 comment characters. | |
| 3294 | 363 |
| 364 After the copyright notice and help text come several @dfn{header | |
| 365 comment} lines, each beginning with @samp{## @var{header-name}:}. For | |
| 366 example, | |
| 367 | |
| 368 @example | |
| 369 @group | |
| 370 ## Author: jwe | |
| 371 ## Keywords: subprocesses input-output | |
| 372 ## Maintainer: jwe | |
| 373 @end group | |
| 374 @end example | |
| 375 | |
| 376 Here is a table of the conventional possibilities for @var{header-name}: | |
| 377 | |
| 378 @table @samp | |
| 379 @item Author | |
| 380 This line states the name and net address of at least the principal | |
| 381 author of the library. | |
| 382 | |
| 6670 | 383 @example |
| 9322 | 384 ## Author: John W. Eaton <jwe@@octave.org> |
| 6670 | 385 @end example |
| 3294 | 386 |
| 387 @item Maintainer | |
| 388 This line should contain a single name/address as in the Author line, or | |
| 389 an address only, or the string @samp{jwe}. If there is no maintainer | |
| 390 line, the person(s) in the Author field are presumed to be the | |
| 391 maintainers. The example above is mildly bogus because the maintainer | |
| 392 line is redundant. | |
| 393 | |
| 394 The idea behind the @samp{Author} and @samp{Maintainer} lines is to make | |
| 395 possible a function to ``send mail to the maintainer'' without | |
| 396 having to mine the name out by hand. | |
| 397 | |
| 398 Be sure to surround the network address with @samp{<@dots{}>} if | |
| 399 you include the person's full name as well as the network address. | |
| 400 | |
| 401 @item Created | |
| 402 This optional line gives the original creation date of the | |
| 403 file. For historical interest only. | |
| 404 | |
| 405 @item Version | |
| 406 If you wish to record version numbers for the individual Octave program, | |
| 407 put them in this line. | |
| 408 | |
| 409 @item Adapted-By | |
| 410 In this header line, place the name of the person who adapted the | |
| 411 library for installation (to make it fit the style conventions, for | |
| 412 example). | |
| 413 | |
| 414 @item Keywords | |
| 415 This line lists keywords. Eventually, it will be used by an apropos | |
| 416 command to allow people will find your package when they're looking for | |
| 417 things by topic area. To separate the keywords, you can use spaces, | |
| 418 commas, or both. | |
| 419 @end table | |
| 420 | |
| 421 Just about every Octave function ought to have the @samp{Author} and | |
| 422 @samp{Keywords} header comment lines. Use the others if they are | |
| 423 appropriate. You can also put in header lines with other header | |
| 424 names---they have no standard meanings, so they can't do any harm. | |
| 6574 | 425 |
| 426 @node Documentation Tips | |
| 427 @section Tips for Documentation Strings | |
| 428 | |
| 429 As noted above, documentation is typically in a commented header block | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
430 on an Octave function following the copyright statement. The help string |
| 7001 | 431 shown above is an unformatted string and will be displayed as is by |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
432 Octave. Here are some tips for the writing of documentation strings. |
| 6574 | 433 |
| 434 @itemize @bullet | |
| 435 @item | |
| 436 Every command, function, or variable intended for users to know about | |
| 437 should have a documentation string. | |
| 438 | |
| 439 @item | |
| 440 An internal variable or subroutine of an Octave program might as well have | |
| 441 a documentation string. | |
| 442 | |
| 443 @item | |
| 444 The first line of the documentation string should consist of one or two | |
| 445 complete sentences that stand on their own as a summary. | |
| 446 | |
| 447 The documentation string can have additional lines that expand on the | |
| 448 details of how to use the function or variable. The additional lines | |
| 449 should also be made up of complete sentences. | |
| 450 | |
| 451 @item | |
| 452 For consistency, phrase the verb in the first sentence of a | |
| 453 documentation string as an infinitive with ``to'' omitted. For | |
| 454 instance, use ``Return the frob of A and B.'' in preference to ``Returns | |
| 455 the frob of A and B@.'' Usually it looks good to do likewise for the | |
| 456 rest of the first paragraph. Subsequent paragraphs usually look better | |
| 457 if they have proper subjects. | |
| 458 | |
| 459 @item | |
| 460 Write documentation strings in the active voice, not the passive, and in | |
| 461 the present tense, not the future. For instance, use ``Return a list | |
| 462 containing A and B.'' instead of ``A list containing A and B will be | |
| 463 returned.'' | |
| 464 | |
| 465 @item | |
| 466 Avoid using the word ``cause'' (or its equivalents) unnecessarily. | |
| 467 Instead of, ``Cause Octave to display text in boldface,'' write just | |
| 468 ``Display text in boldface.'' | |
| 469 | |
| 470 @item | |
| 471 Do not start or end a documentation string with whitespace. | |
| 472 | |
| 473 @item | |
| 474 Format the documentation string so that it fits in an Emacs window on an | |
| 475 80-column screen. It is a good idea for most lines to be no wider than | |
| 476 60 characters. | |
| 477 | |
| 478 However, rather than simply filling the entire documentation string, you | |
| 479 can make it much more readable by choosing line breaks with care. | |
| 480 Use blank lines between topics if the documentation string is long. | |
| 481 | |
| 482 @item | |
| 483 @strong{Do not} indent subsequent lines of a documentation string so | |
| 484 that the text is lined up in the source code with the text of the first | |
| 485 line. This looks nice in the source code, but looks bizarre when users | |
| 486 view the documentation. Remember that the indentation before the | |
| 487 starting double-quote is not part of the string! | |
| 488 | |
| 489 @item | |
| 490 The documentation string for a variable that is a yes-or-no flag should | |
| 491 start with words such as ``Nonzero means@dots{}'', to make it clear that | |
| 492 all nonzero values are equivalent and indicate explicitly what zero and | |
| 493 nonzero mean. | |
| 494 | |
| 495 @item | |
| 496 When a function's documentation string mentions the value of an argument | |
| 497 of the function, use the argument name in capital letters as if it were | |
| 498 a name for that value. Thus, the documentation string of the operator | |
| 499 @code{/} refers to its second argument as @samp{DIVISOR}, because the | |
| 500 actual argument name is @code{divisor}. | |
| 501 | |
| 502 Also use all caps for meta-syntactic variables, such as when you show | |
| 503 the decomposition of a list or vector into subunits, some of which may | |
| 504 vary. | |
| 505 @end itemize | |
| 506 | |
| 507 Octave also allows extensive formatting of the help string of functions | |
| 508 using Texinfo. The effect on the online documentation is relatively | |
| 509 small, but makes the help string of functions conform to the help of | |
| 510 Octave's own functions. However, the effect on the appearance of printed | |
| 511 or online documentation will be greatly improved. | |
| 512 | |
| 513 The fundamental building block of Texinfo documentation strings is the | |
| 514 Texinfo-macro @code{@@deftypefn}, which takes three arguments: The class | |
| 515 the function is in, its output arguments, and the function's | |
| 516 signature. Typical classes for functions include @code{Function File} | |
| 517 for standard Octave functions, and @code{Loadable Function} for | |
| 518 dynamically linked functions. A skeletal Texinfo documentation string | |
| 519 therefore looks like this | |
| 520 | |
| 521 @example | |
| 522 @group | |
| 523 -*- texinfo -*- | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
524 @@deftypefn@{Function File@} @{@@var@{ret@} =@} fn (@dots{}) |
| 6574 | 525 @@cindex index term |
| 7081 | 526 Help text in Texinfo format. Code samples should be marked |
| 527 like @@code@{sample of code@} and variables should be marked | |
| 528 as @@var@{variable@}. | |
| 529 @@seealso@{fn2@} | |
| 6574 | 530 @@end deftypefn |
| 531 @end group | |
| 532 @end example | |
| 533 | |
| 534 This help string must be commented in user functions, or in the help | |
|
9209
923c7cb7f13f
Simplify TeXinfo files by eliminating redundant @iftex followed by @tex construction.
Rik <rdrider0-list@yahoo.com>
parents:
9080
diff
changeset
|
535 string of the @w{@code{DEFUN_DLD}} macro for dynamically loadable |
| 6574 | 536 functions. The important aspects of the documentation string are |
| 537 | |
| 538 @table @asis | |
|
10791
3140cb7a05a1
Add spellchecker scripts for Octave and run spellcheck of documentation
Rik <octave@nomad.inbox5.com>
parents:
10284
diff
changeset
|
539 @item -*- @nospell{texinfo} -*- |
|
8347
fa78cb8d8a5c
corrections for typos
Brian Gough<bjg@network-theory.co.uk>
parents:
7768
diff
changeset
|
540 This string signals Octave that the following text is in Texinfo format, |
| 6574 | 541 and should be the first part of any help string in Texinfo format. |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
542 |
| 6574 | 543 @item @@deftypefn@{class@} @dots{} @@end deftypefn |
| 544 The entire help string should be enclosed within the block defined by | |
| 545 deftypefn. | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
546 |
| 6574 | 547 @item @@cindex index term |
| 548 This generates an index entry, and can be useful when the function is | |
| 549 included as part of a larger piece of documentation. It is ignored | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
550 within Octave's help viewer. Only one index term may appear per line |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
551 but multiple @@cindex lines are valid if the function should be |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
552 filed under different terms. |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
553 |
| 6574 | 554 @item @@var@{variable@} |
| 555 All variables should be marked with this macro. The markup of variables | |
| 556 is then changed appropriately for display. | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
557 |
| 6574 | 558 @item @@code@{sample of code@} |
| 559 All samples of code should be marked with this macro for the same | |
| 560 reasons as the @@var macro. | |
|
10828
322f43e0e170
Grammarcheck .txi documentation files.
Rik <octave@nomad.inbox5.com>
parents:
10812
diff
changeset
|
561 |
| 6574 | 562 @item @@seealso@{function2@} |
| 563 This is a comma separated list of function names that allows cross | |
| 564 referencing from one function documentation string to another. | |
| 565 @end table | |
| 566 | |
| 567 Texinfo format has been designed to generate output for online viewing | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
568 with text terminals as well as generating high-quality printed output. |
| 6574 | 569 To these ends, Texinfo has commands which control the diversion of parts |
| 570 of the document into a particular output processor. Three formats are | |
|
10791
3140cb7a05a1
Add spellchecker scripts for Octave and run spellcheck of documentation
Rik <octave@nomad.inbox5.com>
parents:
10284
diff
changeset
|
571 of importance: info, HTML and @TeX{}. These are selected with |
| 6574 | 572 |
| 573 @example | |
| 574 @group | |
| 575 @@ifinfo | |
| 576 Text area for info only | |
| 577 @@end ifinfo | |
| 578 @end group | |
| 579 @end example | |
| 580 | |
| 581 @example | |
| 582 @group | |
| 583 @@ifhtml | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
584 Text area for HTML only |
| 6574 | 585 @@end ifhtml |
| 586 @end group | |
| 587 @end example | |
| 588 | |
| 589 @example | |
| 590 @group | |
| 591 @@tex | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
592 Text area for TeX only |
| 6574 | 593 @@end tex |
| 594 @end group | |
| 595 @end example | |
| 596 | |
|
10791
3140cb7a05a1
Add spellchecker scripts for Octave and run spellcheck of documentation
Rik <octave@nomad.inbox5.com>
parents:
10284
diff
changeset
|
597 Note that often @TeX{} output can be used in HTML documents and so often |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
598 the @code{@@ifhtml} blocks are unnecessary. If no specific output |
| 6574 | 599 processor is chosen, by default, the text goes into all output |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
600 processors. It is usual to have the above blocks in pairs to allow the |
| 6574 | 601 same information to be conveyed in all output formats, but with a |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
602 different markup. Currently, most Octave documentation only makes a |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
603 distinction between @TeX{} and all other formats. Therefore, the |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
604 following construct is seen repeatedly. |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
605 |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
606 @example |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
607 @group |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
608 @@tex |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
609 text for TeX only |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
610 @@end tex |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
611 @@ifnottex |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
612 text for info, HTML, plaintext |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
613 @@end ifnottex |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
614 @end group |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
615 @end example |
| 6574 | 616 |
| 617 Another important feature of Texinfo that is often used in Octave help | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
618 strings is the @code{@@example} environment. An example of its use is |
| 6574 | 619 |
| 620 @example | |
| 621 @group | |
| 622 @@example | |
| 623 @@group | |
| 624 @@code@{2 * 2@} | |
| 625 @@result@{@} 4 | |
| 626 @@end group | |
| 627 @@end example | |
| 628 @end group | |
| 629 @end example | |
| 630 | |
|
10846
a4f482e66b65
Grammarcheck more of the documentation.
Rik <octave@nomad.inbox5.com>
parents:
10828
diff
changeset
|
631 @noindent |
| 6574 | 632 which produces |
| 633 | |
| 634 @example | |
| 635 @group | |
| 636 @code{2 * 2} | |
| 637 @result{} 4 | |
| 638 @end group | |
| 639 @end example | |
| 640 | |
| 641 The @code{@@group} block prevents the example from being split across a | |
| 642 page boundary, while the @code{@@result@{@}} macro produces a right | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
643 arrow signifying the result of a command. If your example is larger than |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
644 20 lines it is better NOT to use grouping so that a reasonable page boundary |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
645 can be calculated. |
| 6574 | 646 |
| 8828 | 647 In many cases a function has multiple ways in which it can be called, |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
648 and the @code{@@deftypefnx} macro can be used to give alternatives. For |
| 6574 | 649 example |
| 650 | |
| 651 @example | |
| 652 @group | |
| 653 -*- texinfo -*- | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
654 @@deftypefn@{Function File@} @{@@var@{a@} =@} fn (@@var@{x@}, @dots{}) |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
655 @@deftypefnx@{Function File@} @{@@var@{a@} =@} fn (@@var@{y@}, @dots{}) |
| 6574 | 656 Help text in Texinfo format. |
| 657 @@end deftypefn | |
| 658 @end group | |
| 659 @end example | |
| 660 | |
| 661 Many complete examples of Texinfo documentation can be taken from the | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
662 help strings for the Octave functions themselves. A relatively complete |
|
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
663 example of which is the @code{nchoosek} function. The Texinfo |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
664 documentation string for @code{nchoosek} is |
| 6574 | 665 |
| 666 @example | |
| 667 -*- texinfo -*- | |
| 7081 | 668 @@deftypefn @{Function File@} @{@} nchoosek (@@var@{n@}, @@var@{k@}) |
| 6574 | 669 |
| 7081 | 670 Compute the binomial coefficient or all combinations of |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
671 @@var@{n@}. If @@var@{n@} is a scalar then, calculate the |
| 7081 | 672 binomial coefficient of @@var@{n@} and @@var@{k@}, defined as |
| 6574 | 673 |
| 674 @@tex | |
| 675 $$ | |
| 676 @{n \choose k@} = @{n (n-1) (n-2) \cdots (n-k+1) \over k!@} | |
| 677 $$ | |
| 678 @@end tex | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
679 @@ifnottex |
| 6574 | 680 |
| 681 @@example | |
| 682 @@group | |
| 683 / \ | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
684 | n | n (n-1) (n-2) @dots{} (n-k+1) |
| 6574 | 685 | | = ------------------------- |
| 686 | k | k! | |
| 687 \ / | |
| 688 @@end group | |
| 689 @@end example | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
690 @@end ifnottex |
| 6574 | 691 |
| 7081 | 692 If @@var@{n@} is a vector, this generates all combinations |
| 693 of the elements of @@var@{n@}, taken @@var@{k@} at a time, | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
694 one row per combination. The resulting @@var@{c@} has size |
| 7081 | 695 @@code@{[nchoosek (length (@@var@{n@}),@@var@{k@}), @@var@{k@}]@}. |
| 6574 | 696 |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
697 @@code@{nchoosek@} works only for non-negative integer arguments; use |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
698 @@code@{bincoeff@} for non-integer scalar arguments and for using vector |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
699 arguments to compute many coefficients at once. |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
700 |
| 6574 | 701 @@seealso@{bincoeff@} |
| 702 @@end deftypefn | |
| 703 @end example | |
| 704 | |
| 705 which demonstrates most of the concepts discussed above. | |
| 706 @iftex | |
| 707 This documentation string renders as | |
| 708 | |
| 709 @c Note actually use the output of info below rather than try and | |
| 710 @c reproduce it here to prevent it looking different than how it would | |
| 711 @c appear with info. | |
| 712 @example | |
| 713 @group | |
| 714 -- Function File: C = nchoosek (N, K) | |
| 7081 | 715 Compute the binomial coefficient or all combinations |
| 716 of N. If N is a scalar then, calculate the binomial | |
| 717 coefficient of N and K, defined as | |
| 6574 | 718 |
| 719 / \ | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
720 | n | n (n-1) (n-2) @dots{} (n-k+1) n! |
| 7081 | 721 | | = ------------------------- = --------- |
| 722 | k | k! k! (n-k)! | |
| 6574 | 723 \ / |
| 724 | |
| 7081 | 725 If N is a vector generate all combinations of the |
| 726 elements of N, taken K at a time, one row per | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
727 combination. The resulting C has size `[nchoosek |
| 7081 | 728 (length (N), K), K]'. |
| 6574 | 729 |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
730 `nchoosek' works only for non-negative integer |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
731 arguments; use `bincoeff' for non-integer scalar |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
732 arguments and for using vector arguments to compute |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
733 many coefficients at once. |
| 6574 | 734 |
| 735 See also: bincoeff. | |
| 736 @end group | |
| 737 @end example | |
| 738 | |
|
9209
923c7cb7f13f
Simplify TeXinfo files by eliminating redundant @iftex followed by @tex construction.
Rik <rdrider0-list@yahoo.com>
parents:
9080
diff
changeset
|
739 using info, whereas in a printed documentation using @TeX{} it will appear |
| 6574 | 740 as |
| 741 | |
| 742 @deftypefn {Function File} {@var{c} =} nchoosek (@var{n}, @var{k}) | |
| 743 | |
| 6576 | 744 Compute the binomial coefficient or all combinations of @var{n}. |
| 6574 | 745 If @var{n} is a scalar then, calculate the binomial coefficient |
| 746 of @var{n} and @var{k}, defined as | |
| 747 | |
| 748 @tex | |
| 749 $$ | |
| 750 {n \choose k} = {n (n-1) (n-2) \cdots (n-k+1) \over k!} | |
| 751 $$ | |
| 752 @end tex | |
| 753 | |
| 754 If @var{n} is a vector generate all combinations of the elements | |
|
9080
ec41eabf4499
Cleanup documentation files dynamic.texi, testfun.texi, tips.texi
Rik <rdrider0-list@yahoo.com>
parents:
9038
diff
changeset
|
755 of @var{n}, taken @var{k} at a time, one row per combination. The |
| 6574 | 756 resulting @var{c} has size @code{[nchoosek (length (@var{n}), |
| 757 @var{k}), @var{k}]}. | |
| 758 | |
|
9210
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
759 @code{nchoosek} works only for non-negative integer arguments; use |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
760 @code{bincoeff} for non-integer scalar arguments and for using vector |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
761 arguments to compute many coefficients at once. |
|
a7a9eecc07b5
Change recommendation for writing documentation to favor @tex
Rik <rdrider0-list@yahoo.com>
parents:
9209
diff
changeset
|
762 |
| 6574 | 763 @seealso{bincoeff} |
| 764 @end deftypefn | |
| 765 | |
| 766 @end iftex |