Mercurial > octave-nkf
annotate doc/interpreter/intro.txi @ 8476:4998c6c78632
[docs] fix case to match example
| author | Brian Gough <bjg@gnu.org> |
|---|---|
| date | Tue, 13 Jan 2009 00:23:28 -0500 |
| parents | 0b1521bc9afa |
| children | eb63fbe60fab |
| rev | line source |
|---|---|
| 6778 | 1 @c Copyright (C) 1996, 1997, 2007 John W. Eaton |
| 7018 | 2 @c |
| 3 @c This file is part of Octave. | |
| 4 @c | |
| 5 @c Octave is free software; you can redistribute it and/or modify it | |
| 6 @c under the terms of the GNU General Public License as published by the | |
| 7 @c Free Software Foundation; either version 3 of the License, or (at | |
| 8 @c your option) any later version. | |
| 9 @c | |
| 10 @c Octave is distributed in the hope that it will be useful, but WITHOUT | |
| 11 @c ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 12 @c FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 13 @c for more details. | |
| 14 @c | |
| 15 @c You should have received a copy of the GNU General Public License | |
| 16 @c along with Octave; see the file COPYING. If not, see | |
| 17 @c <http://www.gnu.org/licenses/>. | |
| 3294 | 18 |
| 4167 | 19 @node Introduction |
| 3294 | 20 @chapter A Brief Introduction to Octave |
| 21 @cindex introduction | |
| 22 | |
| 6620 | 23 This manual documents how to install, run, and use GNU Octave, and how |
| 3294 | 24 to report bugs. |
| 25 | |
| 26 GNU Octave is a high-level language, primarily intended for numerical | |
| 27 computations. It provides a convenient command line interface for | |
| 28 solving linear and nonlinear problems numerically, and for performing | |
| 29 other numerical experiments. It may also be used as a batch-oriented | |
| 30 language. | |
| 31 | |
| 32 GNU Octave is also freely redistributable software. You may | |
| 33 redistribute it and/or modify it under the terms of the GNU General | |
| 34 Public License as published by the Free Software Foundation. The GPL is | |
| 35 included in this manual in @ref{Copying}. | |
| 36 | |
| 37 This document corresponds to Octave version @value{VERSION}. | |
| 38 | |
| 5775 | 39 @c FIXME -- add explanation about how and why Octave was written. |
| 3294 | 40 @c |
| 5775 | 41 @c FIXME -- add a sentence or two explaining that we could |
| 3294 | 42 @c always use more funding. |
| 43 | |
| 44 @menu | |
| 45 * Running Octave:: | |
| 46 * Simple Examples:: | |
| 47 * Conventions:: | |
| 48 @end menu | |
| 49 | |
| 4167 | 50 @node Running Octave |
| 3294 | 51 @section Running Octave |
| 52 | |
| 53 On most systems, the way to invoke Octave is with the shell command | |
| 54 @samp{octave}. Octave displays an initial message and then a prompt | |
| 55 indicating it is ready to accept input. You can begin typing Octave | |
| 56 commands immediately afterward. | |
| 57 | |
| 58 If you get into trouble, you can usually interrupt Octave by typing | |
| 59 @kbd{Control-C} (usually written @kbd{C-c} for short). @kbd{C-c} gets | |
| 60 its name from the fact that you type it by holding down @key{CTRL} and | |
| 61 then pressing @key{c}. Doing this will normally return you to Octave's | |
| 62 prompt. | |
| 63 | |
| 64 @cindex exiting octave | |
| 65 @cindex quitting octave | |
| 66 To exit Octave, type @kbd{quit}, or @kbd{exit} at the Octave prompt. | |
| 67 | |
| 68 On systems that support job control, you can suspend Octave by sending | |
| 69 it a @code{SIGTSTP} signal, usually by typing @kbd{C-z}. | |
| 70 | |
| 4167 | 71 @node Simple Examples |
| 3294 | 72 @section Simple Examples |
| 73 | |
| 74 The following chapters describe all of Octave's features in detail, but | |
| 75 before doing that, it might be helpful to give a sampling of some of its | |
| 76 capabilities. | |
| 77 | |
| 78 If you are new to Octave, I recommend that you try these examples to | |
| 79 begin learning Octave by using it. Lines marked with @samp{octave:13>} | |
| 80 are lines you type, ending each with a carriage return. Octave will | |
| 81 respond with an answer, or by displaying a graph. | |
| 82 | |
| 6623 | 83 @subsection Creating a Matrix |
| 3294 | 84 |
| 85 To create a new matrix and store it in a variable so that it you can | |
| 86 refer to it later, type the command | |
| 87 | |
| 88 @example | |
| 6620 | 89 octave:1> A = [ 1, 1, 2; 3, 5, 8; 13, 21, 34 ] |
| 3294 | 90 @end example |
| 91 | |
| 92 @noindent | |
| 93 Octave will respond by printing the matrix in neatly aligned columns. | |
| 94 Ending a command with a semicolon tells Octave to not print the result | |
| 95 of a command. For example | |
| 96 | |
| 97 @example | |
| 6620 | 98 octave:2> B = rand (3, 2); |
| 3294 | 99 @end example |
| 100 | |
| 101 @noindent | |
| 102 will create a 3 row, 2 column matrix with each element set to a random | |
| 103 value between zero and one. | |
| 104 | |
| 105 To display the value of any variable, simply type the name of the | |
| 106 variable. For example, to display the value stored in the matrix | |
| 6620 | 107 @code{B}, type the command |
| 3294 | 108 |
| 109 @example | |
| 6620 | 110 octave:3> B |
| 3294 | 111 @end example |
| 112 | |
| 6623 | 113 @subsection Matrix Arithmetic |
| 3294 | 114 |
| 115 Octave has a convenient operator notation for performing matrix | |
|
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116 arithmetic. For example, to multiply the matrix @code{A} by a scalar |
| 3294 | 117 value, type the command |
| 118 | |
| 119 @example | |
| 6620 | 120 octave:4> 2 * A |
| 3294 | 121 @end example |
| 122 | |
| 6620 | 123 @noindent |
|
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[docs] fix case to match example
Brian Gough <bjg@gnu.org>
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124 To multiply the two matrices @code{A} and @code{B}, type the command |
| 3294 | 125 |
| 126 @example | |
| 6620 | 127 octave:5> A * B |
| 3294 | 128 @end example |
| 129 | |
| 6620 | 130 @noindent |
| 131 and to form the matrix product | |
| 3294 | 132 @iftex |
| 133 @tex | |
| 6620 | 134 $@code{A}^T@code{A}$, |
| 3294 | 135 @end tex |
| 136 @end iftex | |
| 6620 | 137 @ifnottex |
| 138 @code{transpose (A) * A}, | |
| 139 @end ifnottex | |
| 3294 | 140 type the command |
| 141 | |
| 142 @example | |
| 6620 | 143 octave:6> A' * A |
| 3294 | 144 @end example |
| 145 | |
| 6623 | 146 @subsection Solving Linear Equations |
| 3294 | 147 |
| 6620 | 148 To solve the set of linear equations @code{A@var{x} = b}, |
| 3294 | 149 use the left division operator, @samp{\}: |
| 150 | |
| 151 @example | |
| 6620 | 152 octave:7> A \ b |
| 3294 | 153 @end example |
| 154 | |
| 155 @noindent | |
| 156 This is conceptually equivalent to | |
| 157 @iftex | |
| 158 @tex | |
| 6620 | 159 $@code{A}^{-1}@code{b}$, |
| 3294 | 160 @end tex |
| 161 @end iftex | |
| 6620 | 162 @ifnottex |
| 3294 | 163 @code{inv (a) * b}, |
| 6620 | 164 @end ifnottex |
| 3294 | 165 but avoids computing the inverse of a matrix directly. |
| 166 | |
| 167 If the coefficient matrix is singular, Octave will print a warning | |
| 168 message and compute a minimum norm solution. | |
| 169 | |
| 6623 | 170 @subsection Integrating Differential Equations |
| 3294 | 171 |
| 172 Octave has built-in functions for solving nonlinear differential | |
| 173 equations of the form | |
| 174 @iftex | |
| 175 @tex | |
| 176 $$ | |
| 177 {dx \over dt} = f(x,t), \qquad x(t=t_0) = x_0 | |
| 178 $$ | |
| 179 @end tex | |
| 180 @end iftex | |
| 6620 | 181 @ifnottex |
| 3294 | 182 |
| 183 @example | |
| 184 @group | |
| 185 dx | |
| 186 -- = f (x, t) | |
| 187 dt | |
| 188 @end group | |
| 189 @end example | |
| 190 | |
| 191 @noindent | |
| 192 with the initial condition | |
| 193 | |
| 194 @example | |
| 195 x(t = t0) = x0 | |
| 196 @end example | |
| 6620 | 197 @end ifnottex |
| 3294 | 198 |
| 199 @noindent | |
| 200 For Octave to integrate equations of this form, you must first provide a | |
| 201 definition of the function | |
| 202 @iftex | |
| 203 @tex | |
| 204 $f (x, t)$. | |
| 205 @end tex | |
| 206 @end iftex | |
| 6620 | 207 @ifnottex |
| 3294 | 208 @code{f(x,t)}. |
| 6620 | 209 @end ifnottex |
| 3294 | 210 This is straightforward, and may be accomplished by entering the |
| 211 function body directly on the command line. For example, the following | |
| 212 commands define the right hand side function for an interesting pair of | |
| 213 nonlinear differential equations. Note that while you are entering a | |
| 214 function, Octave responds with a different prompt, to indicate that it | |
| 215 is waiting for you to complete your input. | |
| 216 | |
| 217 @example | |
| 218 @group | |
| 219 octave:8> function xdot = f (x, t) | |
| 220 > | |
| 221 > r = 0.25; | |
| 222 > k = 1.4; | |
| 223 > a = 1.5; | |
| 224 > b = 0.16; | |
| 225 > c = 0.9; | |
| 226 > d = 0.8; | |
| 227 > | |
| 228 > xdot(1) = r*x(1)*(1 - x(1)/k) - a*x(1)*x(2)/(1 + b*x(1)); | |
| 229 > xdot(2) = c*a*x(1)*x(2)/(1 + b*x(1)) - d*x(2); | |
| 230 > | |
| 231 > endfunction | |
| 232 @end group | |
| 233 @end example | |
| 234 | |
| 235 @noindent | |
| 236 Given the initial condition | |
| 237 | |
| 238 @example | |
| 239 x0 = [1; 2]; | |
| 240 @end example | |
| 241 | |
| 242 @noindent | |
| 243 and the set of output times as a column vector (note that the first | |
| 244 output time corresponds to the initial condition given above) | |
| 245 | |
| 246 @example | |
| 247 t = linspace (0, 50, 200)'; | |
| 248 @end example | |
| 249 | |
| 250 @noindent | |
| 251 it is easy to integrate the set of differential equations: | |
| 252 | |
| 253 @example | |
| 254 x = lsode ("f", x0, t); | |
| 255 @end example | |
| 256 | |
| 257 @noindent | |
| 258 The function @code{lsode} uses the Livermore Solver for Ordinary | |
| 259 Differential Equations, described in A. C. Hindmarsh, @cite{ODEPACK, a | |
| 260 Systematized Collection of ODE Solvers}, in: Scientific Computing, R. S. | |
| 261 Stepleman et al. (Eds.), North-Holland, Amsterdam, 1983, pages 55--64. | |
| 262 | |
| 6623 | 263 @subsection Producing Graphical Output |
| 3294 | 264 |
| 265 To display the solution of the previous example graphically, use the | |
| 266 command | |
| 267 | |
| 268 @example | |
| 269 plot (t, x) | |
| 270 @end example | |
| 271 | |
| 6620 | 272 @noindent |
| 273 If you are using a graphical user interface, Octave will automatically create | |
| 6331 | 274 a separate window to display the plot. |
| 275 | |
| 6620 | 276 To save a plot once it has been displayed on the screen, use the print |
| 6331 | 277 command. For example, |
| 3294 | 278 |
| 279 @example | |
| 6331 | 280 print -deps foo.eps |
| 3294 | 281 @end example |
| 282 | |
| 283 @noindent | |
| 7001 | 284 will create a file called @file{foo.eps} that contains a rendering of |
| 6331 | 285 the current plot. The command |
| 3294 | 286 |
| 287 @example | |
| 6331 | 288 help print |
| 3294 | 289 @end example |
| 290 | |
| 291 @noindent | |
| 6331 | 292 explains more options for the @code{print} command and provides a list |
| 6620 | 293 of additional output file formats. |
| 3294 | 294 |
| 6623 | 295 @subsection Editing What You Have Typed |
| 3294 | 296 |
| 297 At the Octave prompt, you can recall, edit, and reissue previous | |
| 298 commands using Emacs- or vi-style editing commands. The default | |
| 299 keybindings use Emacs-style commands. For example, to recall the | |
| 6620 | 300 previous command, press @kbd{Control-p} (usually written @kbd{C-p} for |
| 301 short). Doing this will normally bring back the previous line of input. | |
| 302 @kbd{C-n} will bring up the next line of input, @kbd{C-b} will move | |
| 303 the cursor backward on the line, @kbd{C-f} will move the cursor forward | |
| 304 on the line, etc. | |
| 3294 | 305 |
| 306 A complete description of the command line editing capability is given | |
| 307 in this manual in @ref{Command Line Editing}. | |
| 308 | |
| 6623 | 309 @subsection Help and Documentation |
| 3294 | 310 |
| 311 Octave has an extensive help facility. The same documentation that is | |
| 312 available in printed form is also available from the Octave prompt, | |
| 313 because both forms of the documentation are created from the same input | |
| 314 file. | |
| 315 | |
| 316 In order to get good help you first need to know the name of the command | |
| 317 that you want to use. This name of the function may not always be | |
| 318 obvious, but a good place to start is to just type @code{help}. | |
| 319 This will show you all the operators, reserved words, functions, | |
| 6620 | 320 built-in variables, and function files. An alternative is to search the |
| 321 documentation using the @code{lookfor} function. This function is | |
| 322 described in @ref{Getting Help}. | |
| 323 | |
| 324 Once you know the name of the function you wish to use, you can get more | |
| 325 help on the function by simply including the name as an argument to help. | |
| 326 For example, | |
| 3294 | 327 |
| 328 @example | |
| 329 help plot | |
| 330 @end example | |
| 331 | |
| 332 @noindent | |
| 333 will display the help text for the @code{plot} function. | |
| 334 | |
| 335 Octave sends output that is too long to fit on one screen through a | |
| 336 pager like @code{less} or @code{more}. Type a @key{RET} to advance one | |
| 337 line, a @key{SPC} to advance one page, and @key{q} to exit the pager. | |
| 338 | |
| 339 The part of Octave's help facility that allows you to read the complete | |
| 340 text of the printed manual from within Octave normally uses a separate | |
| 341 program called Info. When you invoke Info you will be put into a menu | |
| 342 driven program that contains the entire Octave manual. Help for using | |
| 343 Info is provided in this manual in @ref{Getting Help}. | |
| 344 | |
| 4167 | 345 @node Conventions |
| 3294 | 346 @section Conventions |
| 347 | |
| 348 This section explains the notational conventions that are used in this | |
| 349 manual. You may want to skip this section and refer back to it later. | |
| 350 | |
| 351 @menu | |
| 352 * Fonts:: | |
| 353 * Evaluation Notation:: | |
| 354 * Printing Notation:: | |
| 355 * Error Messages:: | |
| 356 * Format of Descriptions:: | |
| 357 @end menu | |
| 358 | |
| 4167 | 359 @node Fonts |
| 3294 | 360 @subsection Fonts |
| 361 @cindex fonts | |
| 362 | |
| 363 Examples of Octave code appear in this font or form: @code{svd (a)}. | |
| 364 Names that represent arguments or metasyntactic variables appear | |
| 365 in this font or form: @var{first-number}. Commands that you type at the | |
| 366 shell prompt sometimes appear in this font or form: | |
| 367 @samp{octave --no-init-file}. Commands that you type at the Octave | |
| 368 prompt sometimes appear in this font or form: @kbd{foo --bar --baz}. | |
| 369 Specific keys on your keyboard appear in this font or form: @key{ANY}. | |
| 370 @cindex any key | |
| 371 | |
| 4167 | 372 @node Evaluation Notation |
| 3294 | 373 @subsection Evaluation Notation |
| 374 @cindex evaluation notation | |
| 375 @cindex documentation notation | |
| 376 | |
| 377 In the examples in this manual, results from expressions that you | |
| 378 evaluate are indicated with @samp{@result{}}. For example, | |
| 379 | |
| 380 @example | |
| 381 @group | |
| 382 sqrt (2) | |
| 383 @result{} 1.4142 | |
| 384 @end group | |
| 385 @end example | |
| 386 | |
| 387 @noindent | |
| 388 You can read this as ``@code{sqrt (2)} evaluates to 1.4142''. | |
| 389 | |
| 390 In some cases, matrix values that are returned by expressions are | |
| 391 displayed like this | |
| 392 | |
| 393 @example | |
| 394 @group | |
| 395 [1, 2; 3, 4] == [1, 3; 2, 4] | |
| 396 @result{} [ 1, 0; 0, 1 ] | |
| 397 @end group | |
| 398 @end example | |
| 399 | |
| 400 @noindent | |
| 401 and in other cases, they are displayed like this | |
| 402 | |
| 403 @example | |
| 404 @group | |
| 405 eye (3) | |
| 406 @result{} 1 0 0 | |
| 407 0 1 0 | |
| 408 0 0 1 | |
| 409 @end group | |
| 410 @end example | |
| 411 | |
| 412 @noindent | |
| 413 in order to clearly show the structure of the result. | |
| 414 | |
| 415 Sometimes to help describe one expression, another expression is | |
| 416 shown that produces identical results. The exact equivalence of | |
| 417 expressions is indicated with @samp{@equiv{}}. For example, | |
| 418 | |
| 419 @example | |
| 420 @group | |
| 421 rot90 ([1, 2; 3, 4], -1) | |
| 422 @equiv{} | |
| 423 rot90 ([1, 2; 3, 4], 3) | |
| 424 @equiv{} | |
| 425 rot90 ([1, 2; 3, 4], 7) | |
| 426 @end group | |
| 427 @end example | |
| 428 | |
| 4167 | 429 @node Printing Notation |
| 3294 | 430 @subsection Printing Notation |
| 431 @cindex printing notation | |
| 432 | |
| 433 Many of the examples in this manual print text when they are | |
| 434 evaluated. Examples in this manual indicate printed text with | |
| 435 @samp{@print{}}. The value that is returned by evaluating the | |
| 436 expression (here @code{1}) is displayed with @samp{@result{}} and | |
| 437 follows on a separate line. | |
| 438 | |
| 439 @example | |
| 440 @group | |
| 441 printf ("foo %s\n", "bar") | |
| 442 @print{} foo bar | |
| 443 @result{} 1 | |
| 444 @end group | |
| 445 @end example | |
| 446 | |
| 4167 | 447 @node Error Messages |
| 3294 | 448 @subsection Error Messages |
| 449 @cindex error message notation | |
| 450 | |
| 451 Some examples signal errors. This normally displays an error message | |
| 452 on your terminal. Error messages are shown on a line starting with | |
| 453 @code{error:}. | |
| 454 | |
| 455 @example | |
| 456 @group | |
| 7490 | 457 fieldnames ([1, 2; 3, 4]) |
| 458 error: fieldnames: wrong type argument `matrix' | |
| 3294 | 459 @end group |
| 460 @end example | |
| 461 | |
| 4167 | 462 @node Format of Descriptions |
| 3294 | 463 @subsection Format of Descriptions |
| 464 @cindex description format | |
| 465 | |
| 466 Functions, commands, and variables are described in this manual in a | |
| 467 uniform format. The first line of a description contains the name of | |
| 468 the item followed by its arguments, if any. | |
| 469 @ifinfo | |
| 470 The category---function, variable, or whatever---appears at the | |
| 471 beginning of the line. | |
| 472 @end ifinfo | |
| 473 @iftex | |
| 474 The category---function, variable, or whatever---is printed next to the | |
| 475 right margin. | |
| 476 @end iftex | |
| 477 The description follows on succeeding lines, sometimes with examples. | |
| 478 | |
| 479 @menu | |
| 480 * A Sample Function Description:: | |
| 481 * A Sample Command Description:: | |
| 482 * A Sample Variable Description:: | |
| 483 @end menu | |
| 484 | |
| 4167 | 485 @node A Sample Function Description |
| 3294 | 486 @subsubsection A Sample Function Description |
| 487 @cindex function descriptions | |
| 488 | |
| 489 In a function description, the name of the function being described | |
| 490 appears first. It is followed on the same line by a list of parameters. | |
| 491 The names used for the parameters are also used in the body of the | |
| 492 description. | |
| 493 | |
| 494 Here is a description of an imaginary function @code{foo}: | |
| 495 | |
| 496 @deftypefn {Function} {} foo (@var{x}, @var{y}, @dots{}) | |
| 497 The function @code{foo} subtracts @var{x} from @var{y}, then adds the | |
| 498 remaining arguments to the result. If @var{y} is not supplied, then the | |
| 499 number 19 is used by default. | |
| 500 | |
| 501 @example | |
| 502 @group | |
| 503 foo (1, [3, 5], 3, 9) | |
| 504 @result{} [ 14, 16 ] | |
| 505 foo (5) | |
| 506 @result{} 14 | |
| 507 @end group | |
| 508 @end example | |
| 509 | |
| 510 More generally, | |
| 511 | |
| 512 @example | |
| 513 @group | |
| 514 foo (@var{w}, @var{x}, @var{y}, @dots{}) | |
| 515 @equiv{} | |
| 516 @var{x} - @var{w} + @var{y} + @dots{} | |
| 517 @end group | |
| 518 @end example | |
| 519 @end deftypefn | |
| 520 | |
| 521 Any parameter whose name contains the name of a type (e.g., | |
| 522 @var{integer}, @var{integer1} or @var{matrix}) is expected to be of that | |
| 523 type. Parameters named @var{object} may be of any type. Parameters | |
| 524 with other sorts of names (e.g., @var{new_file}) are discussed | |
| 525 specifically in the description of the function. In some sections, | |
| 526 features common to parameters of several functions are described at the | |
| 527 beginning. | |
| 528 | |
| 529 Functions in Octave may be defined in several different ways. The | |
| 7001 | 530 category name for functions may include another name that indicates the |
| 3294 | 531 way that the function is defined. These additional tags include |
| 532 | |
| 533 @table @asis | |
| 6620 | 534 @item Function File |
| 535 @cindex function file | |
| 536 The function described is defined using Octave commands stored in a text | |
| 537 file. @xref{Function Files}. | |
| 538 | |
| 3294 | 539 @item Built-in Function |
| 540 @cindex built-in function | |
| 541 The function described is written in a language like C++, C, or Fortran, | |
| 542 and is part of the compiled Octave binary. | |
| 543 | |
| 544 @item Loadable Function | |
| 545 @cindex loadable function | |
| 546 The function described is written in a language like C++, C, or Fortran. | |
| 547 On systems that support dynamic linking of user-supplied functions, it | |
| 548 may be automatically linked while Octave is running, but only if it is | |
| 549 needed. @xref{Dynamically Linked Functions}. | |
| 550 | |
| 551 @item Mapping Function | |
| 552 @cindex mapping function | |
| 553 The function described works element-by-element for matrix and vector | |
| 554 arguments. | |
| 555 @end table | |
| 556 | |
| 4167 | 557 @node A Sample Command Description |
| 3294 | 558 @subsubsection A Sample Command Description |
| 559 @cindex command descriptions | |
| 560 | |
| 561 Command descriptions have a format similar to function descriptions, | |
| 562 except that the word `Function' is replaced by `Command. Commands are | |
| 7001 | 563 functions that may be called without surrounding their arguments in |
| 3294 | 564 parentheses. For example, here is the description for Octave's |
| 565 @code{cd} command: | |
| 566 | |
| 567 @deffn {Command} cd dir | |
| 568 @deffnx {Command} chdir dir | |
| 569 Change the current working directory to @var{dir}. For example, | |
| 570 @kbd{cd ~/octave} changes the current working directory to | |
| 571 @file{~/octave}. If the directory does not exist, an error message is | |
| 572 printed and the working directory is not changed. | |
| 573 @end deffn | |
| 574 | |
| 4167 | 575 @node A Sample Variable Description |
| 3294 | 576 @subsubsection A Sample Variable Description |
| 577 @cindex variable descriptions | |
| 578 | |
| 579 A @dfn{variable} is a name that can hold a value. Although any variable | |
| 580 can be set by the user, @dfn{built-in variables} typically exist | |
| 581 specifically so that users can change them to alter the way Octave | |
| 582 behaves (built-in variables are also sometimes called @dfn{user | |
| 583 options}). Ordinary variables and built-in variables are described | |
| 584 using a format like that for functions except that there are no | |
| 585 arguments. | |
| 586 | |
| 587 Here is a description of the imaginary variable | |
| 588 @code{do_what_i_mean_not_what_i_say}. | |
| 589 | |
| 590 @defvr {Built-in Variable} do_what_i_mean_not_what_i_say | |
| 591 If the value of this variable is nonzero, Octave will do what you | |
| 592 actually wanted, even if you have typed a completely different and | |
| 593 meaningless list of commands. | |
| 594 @end defvr | |
| 595 | |
| 596 Other variable descriptions have the same format, but `Built-in | |
| 597 Variable' is replaced by `Variable', for ordinary variables, or | |
| 598 `Constant' for symbolic constants whose values cannot be changed. |