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annotate doc/interpreter/intro.txi @ 17957:e5566719e0a1
doc: Mention GUI in introduction. Update figure root properties.
* intro.txi: Mention GUI in introduction.
* plot.txi: Update figure root properties.
| author | Michael Godfrey <michaeldgodfrey@gmail.com> |
|---|---|
| date | Sun, 10 Nov 2013 11:06:58 -0500 |
| parents | dae2230227a7 |
| children |
| rev | line source |
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1 @c Copyright (C) 1996-2013 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 | |
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23 GNU Octave is a high-level language, primarily intended for numerical |
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24 computations. It is typically used for such problems as solving |
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25 linear and nonlinear equations, numerical linear algebra, statistical |
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26 analysis, and for performing other numerical experiments. It may also |
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27 be used as a batch-oriented language for automated data processing. |
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28 |
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29 Until recently GNU Octave provided a command-line interface with |
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30 graphical results displayed in separate windows. The current version |
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31 (version 3.8, released in late 2013) also provides, by default, a |
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32 graphical user interface. |
| 3294 | 33 |
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34 GNU Octave is freely redistributable software. You may redistribute |
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35 it and/or modify it under the terms of the GNU General Public License |
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36 as published by the Free Software Foundation. The GPL is included in |
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37 this manual, @pxref{Copying}. |
| 3294 | 38 |
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39 This manual provides comprehensive documentation on how to install, |
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40 run, use, and extend GNU Octave. Additional chapters describe how |
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41 to report bugs and help contribute code. |
| 3294 | 42 |
| 43 This document corresponds to Octave version @value{VERSION}. | |
| 44 | |
| 45 @menu | |
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46 * Running Octave:: |
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47 * Simple Examples:: |
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48 * Conventions:: |
| 3294 | 49 @end menu |
| 50 | |
| 4167 | 51 @node Running Octave |
| 3294 | 52 @section Running Octave |
| 53 | |
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54 On most systems, Octave is started with the shell command @samp{octave}. |
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55 This, by default, starts the graphical user interface (GUI). The central |
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56 window in the GUI is the Octave command-line interface. Octave displays |
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57 an initial message and then a prompt indicating it is ready to accept |
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58 input. If you have chosen the traditional command-line interface only |
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59 the command prompt appears. In any case, you can immediately begin |
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60 typing Octave commands. |
| 3294 | 61 |
| 62 If you get into trouble, you can usually interrupt Octave by typing | |
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63 @kbd{Control-C} (written @kbd{C-c} for short). @kbd{C-c} gets |
| 3294 | 64 its name from the fact that you type it by holding down @key{CTRL} and |
| 65 then pressing @key{c}. Doing this will normally return you to Octave's | |
| 66 prompt. | |
| 67 | |
| 68 @cindex exiting octave | |
| 69 @cindex quitting octave | |
| 70 To exit Octave, type @kbd{quit}, or @kbd{exit} at the Octave prompt. | |
| 71 | |
| 72 On systems that support job control, you can suspend Octave by sending | |
| 73 it a @code{SIGTSTP} signal, usually by typing @kbd{C-z}. | |
| 74 | |
| 4167 | 75 @node Simple Examples |
| 3294 | 76 @section Simple Examples |
| 77 | |
| 78 The following chapters describe all of Octave's features in detail, but | |
| 79 before doing that, it might be helpful to give a sampling of some of its | |
| 80 capabilities. | |
| 81 | |
| 82 If you are new to Octave, I recommend that you try these examples to | |
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83 begin learning Octave by using it. Lines marked like so, @samp{octave:13>}, |
| 3294 | 84 are lines you type, ending each with a carriage return. Octave will |
| 85 respond with an answer, or by displaying a graph. | |
| 86 | |
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87 @subsection Elementary Calculations |
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88 |
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89 Octave can easily be used for basic numerical calculations. Octave |
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90 knows about arithmetic operations (+,-,*,/), exponentiation (^), |
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91 natural logarithms/exponents (log, exp), and the trigonometric |
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92 functions (sin, cos, @dots{}). Moreover, Octave calculations work |
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93 on real or imaginary numbers (i,j). In addition, some mathematical |
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94 constants such as the base of the natural logarithm (e) and the ratio |
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95 of a circle's circumference to its diameter (pi) are pre-defined. |
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96 |
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97 @noindent |
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98 For example, to verify Euler's Identity, |
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99 @tex |
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100 $$e^{\imath\pi} = -1$$ |
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101 @end tex |
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102 @ifnottex |
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103 @display |
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104 |
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105 i*pi |
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106 e = -1 |
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107 @end display |
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108 @end ifnottex |
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109 |
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110 @noindent |
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111 type the following which will evaluate to @code{-1} within the |
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112 tolerance of the calculation. |
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113 |
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114 @example |
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115 octave:1> exp (i*pi) |
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116 @end example |
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117 |
| 6623 | 118 @subsection Creating a Matrix |
| 3294 | 119 |
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120 Vectors and matrices are the basic building blocks for numerical analysis. |
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121 To create a new matrix and store it in a variable so that you can |
| 3294 | 122 refer to it later, type the command |
| 123 | |
| 124 @example | |
| 6620 | 125 octave:1> A = [ 1, 1, 2; 3, 5, 8; 13, 21, 34 ] |
| 3294 | 126 @end example |
| 127 | |
| 128 @noindent | |
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129 Octave will respond by printing the matrix in neatly aligned columns. |
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130 Octave uses a comma or space to separate entries in a row, and a |
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131 semicolon or carriage return to separate one row from the next. |
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132 Ending a command with a semicolon tells Octave not to print the result |
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133 of the command. For example, |
| 3294 | 134 |
| 135 @example | |
| 6620 | 136 octave:2> B = rand (3, 2); |
| 3294 | 137 @end example |
| 138 | |
| 139 @noindent | |
| 140 will create a 3 row, 2 column matrix with each element set to a random | |
| 141 value between zero and one. | |
| 142 | |
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143 To display the value of a variable, simply type the name of the |
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144 variable at the prompt. For example, to display the value stored in the |
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145 matrix @code{B}, type the command |
| 3294 | 146 |
| 147 @example | |
| 6620 | 148 octave:3> B |
| 3294 | 149 @end example |
| 150 | |
| 6623 | 151 @subsection Matrix Arithmetic |
| 3294 | 152 |
| 153 Octave has a convenient operator notation for performing matrix | |
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154 arithmetic. For example, to multiply the matrix @code{A} by a scalar |
| 3294 | 155 value, type the command |
| 156 | |
| 157 @example | |
| 6620 | 158 octave:4> 2 * A |
| 3294 | 159 @end example |
| 160 | |
| 6620 | 161 @noindent |
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162 To multiply the two matrices @code{A} and @code{B}, type the command |
| 3294 | 163 |
| 164 @example | |
| 6620 | 165 octave:5> A * B |
| 3294 | 166 @end example |
| 167 | |
| 6620 | 168 @noindent |
| 169 and to form the matrix product | |
| 3294 | 170 @tex |
| 6620 | 171 $@code{A}^T@code{A}$, |
| 3294 | 172 @end tex |
| 6620 | 173 @ifnottex |
| 174 @code{transpose (A) * A}, | |
| 175 @end ifnottex | |
| 3294 | 176 type the command |
| 177 | |
| 178 @example | |
| 6620 | 179 octave:6> A' * A |
| 3294 | 180 @end example |
| 181 | |
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182 @subsection Solving Systems of Linear Equations |
| 3294 | 183 |
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184 Systems of linear equations are ubiquitous in numerical analysis. |
| 6620 | 185 To solve the set of linear equations @code{A@var{x} = b}, |
| 3294 | 186 use the left division operator, @samp{\}: |
| 187 | |
| 188 @example | |
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189 @var{x} = A \ b |
| 3294 | 190 @end example |
| 191 | |
| 192 @noindent | |
| 193 This is conceptually equivalent to | |
| 194 @tex | |
| 6620 | 195 $@code{A}^{-1}@code{b}$, |
| 3294 | 196 @end tex |
| 6620 | 197 @ifnottex |
| 3294 | 198 @code{inv (a) * b}, |
| 6620 | 199 @end ifnottex |
| 3294 | 200 but avoids computing the inverse of a matrix directly. |
| 201 | |
| 202 If the coefficient matrix is singular, Octave will print a warning | |
| 203 message and compute a minimum norm solution. | |
| 204 | |
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205 A simple example comes from chemistry and the need to obtain balanced |
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206 chemical equations. Consider the burning of hydrogen and oxygen to |
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207 produce water. |
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208 @tex |
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209 $$ {\rm H_{2}} + {\rm O_{2}} \rightarrow {\rm H_{2}O} $$ |
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210 @end tex |
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211 @ifnottex |
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212 |
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213 @example |
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214 H2 + O2 --> H2O |
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215 @end example |
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216 |
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217 @end ifnottex |
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218 @noindent |
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219 The equation above is not accurate. The Law of Conservation of Mass requires |
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220 that the number of molecules of each type balance on the left- and right-hand |
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221 sides of the equation. Writing the variable overall reaction with |
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222 individual equations for hydrogen and oxygen one finds: |
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223 @tex |
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224 \vbox{ |
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225 $$ x_{1}{\rm H_{2}} + x_{2}{\rm O_{2}} \rightarrow {\rm H_{2}O} $$ |
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226 $$ {\rm H:}\quad 2x_{1} + 0x_{2} \rightarrow 2 $$ |
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227 $$ {\rm O:}\quad 0x_{1} + 2x_{2} \rightarrow 1 $$ |
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228 } |
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229 @end tex |
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230 @ifnottex |
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231 |
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232 @example |
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233 @group |
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234 x1*H2 + x2*O2 --> H2O |
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235 H: 2*x1 + 0*x2 --> 2 |
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236 O: 0*x1 + 2*x2 --> 1 |
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237 @end group |
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238 @end example |
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239 |
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240 @end ifnottex |
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241 @noindent |
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242 The solution in Octave is found in just three steps. |
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243 |
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244 @example |
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245 @group |
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246 octave:1> A = [ 2, 0; 0, 2 ]; |
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247 octave:2> b = [ 2; 1 ]; |
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248 octave:3> x = A \ b |
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249 @end group |
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250 @end example |
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251 |
| 6623 | 252 @subsection Integrating Differential Equations |
| 3294 | 253 |
| 254 Octave has built-in functions for solving nonlinear differential | |
| 255 equations of the form | |
| 256 @tex | |
| 257 $$ | |
| 258 {dx \over dt} = f(x,t), \qquad x(t=t_0) = x_0 | |
| 259 $$ | |
| 260 @end tex | |
| 6620 | 261 @ifnottex |
| 3294 | 262 |
| 263 @example | |
| 264 @group | |
| 265 dx | |
| 266 -- = f (x, t) | |
| 267 dt | |
| 268 @end group | |
| 269 @end example | |
| 270 | |
| 271 @noindent | |
| 272 with the initial condition | |
| 273 | |
| 274 @example | |
| 275 x(t = t0) = x0 | |
| 276 @end example | |
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277 |
| 6620 | 278 @end ifnottex |
| 3294 | 279 @noindent |
| 280 For Octave to integrate equations of this form, you must first provide a | |
| 281 definition of the function | |
| 282 @tex | |
| 283 $f (x, t)$. | |
| 284 @end tex | |
| 6620 | 285 @ifnottex |
| 3294 | 286 @code{f(x,t)}. |
| 6620 | 287 @end ifnottex |
| 3294 | 288 This is straightforward, and may be accomplished by entering the |
| 289 function body directly on the command line. For example, the following | |
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290 commands define the right-hand side function for an interesting pair of |
| 3294 | 291 nonlinear differential equations. Note that while you are entering a |
| 292 function, Octave responds with a different prompt, to indicate that it | |
| 293 is waiting for you to complete your input. | |
| 294 | |
| 295 @example | |
| 296 @group | |
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297 octave:1> function xdot = f (x, t) |
| 3294 | 298 > |
| 299 > r = 0.25; | |
| 300 > k = 1.4; | |
| 301 > a = 1.5; | |
| 302 > b = 0.16; | |
| 303 > c = 0.9; | |
| 304 > d = 0.8; | |
| 305 > | |
| 306 > xdot(1) = r*x(1)*(1 - x(1)/k) - a*x(1)*x(2)/(1 + b*x(1)); | |
| 307 > xdot(2) = c*a*x(1)*x(2)/(1 + b*x(1)) - d*x(2); | |
| 308 > | |
| 309 > endfunction | |
| 310 @end group | |
| 311 @end example | |
| 312 | |
| 313 @noindent | |
| 314 Given the initial condition | |
| 315 | |
| 316 @example | |
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317 octave:2> x0 = [1; 2]; |
| 3294 | 318 @end example |
| 319 | |
| 320 @noindent | |
| 321 and the set of output times as a column vector (note that the first | |
| 322 output time corresponds to the initial condition given above) | |
| 323 | |
| 324 @example | |
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325 octave:3> t = linspace (0, 50, 200)'; |
| 3294 | 326 @end example |
| 327 | |
| 328 @noindent | |
| 329 it is easy to integrate the set of differential equations: | |
| 330 | |
| 331 @example | |
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332 octave:4> x = lsode ("f", x0, t); |
| 3294 | 333 @end example |
| 334 | |
| 335 @noindent | |
| 336 The function @code{lsode} uses the Livermore Solver for Ordinary | |
| 337 Differential Equations, described in A. C. Hindmarsh, @cite{ODEPACK, a | |
| 338 Systematized Collection of ODE Solvers}, in: Scientific Computing, R. S. | |
| 339 Stepleman et al. (Eds.), North-Holland, Amsterdam, 1983, pages 55--64. | |
| 340 | |
| 6623 | 341 @subsection Producing Graphical Output |
| 3294 | 342 |
| 343 To display the solution of the previous example graphically, use the | |
| 344 command | |
| 345 | |
| 346 @example | |
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347 octave:1> plot (t, x) |
| 3294 | 348 @end example |
| 349 | |
| 6620 | 350 @noindent |
| 351 If you are using a graphical user interface, Octave will automatically create | |
| 6331 | 352 a separate window to display the plot. |
| 353 | |
| 6620 | 354 To save a plot once it has been displayed on the screen, use the print |
| 6331 | 355 command. For example, |
| 3294 | 356 |
| 357 @example | |
| 6331 | 358 print -deps foo.eps |
| 3294 | 359 @end example |
| 360 | |
| 361 @noindent | |
| 7001 | 362 will create a file called @file{foo.eps} that contains a rendering of |
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363 the current plot in Encapsulated PostScript format. The command |
| 3294 | 364 |
| 365 @example | |
| 6331 | 366 help print |
| 3294 | 367 @end example |
| 368 | |
| 369 @noindent | |
| 6331 | 370 explains more options for the @code{print} command and provides a list |
| 6620 | 371 of additional output file formats. |
| 3294 | 372 |
| 6623 | 373 @subsection Editing What You Have Typed |
| 3294 | 374 |
| 375 At the Octave prompt, you can recall, edit, and reissue previous | |
| 376 commands using Emacs- or vi-style editing commands. The default | |
| 377 keybindings use Emacs-style commands. For example, to recall the | |
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378 previous command, press @kbd{Control-p} (written @kbd{C-p} for |
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379 short). Doing this will normally bring back the previous line of input. |
| 6620 | 380 @kbd{C-n} will bring up the next line of input, @kbd{C-b} will move |
| 381 the cursor backward on the line, @kbd{C-f} will move the cursor forward | |
| 382 on the line, etc. | |
| 3294 | 383 |
| 384 A complete description of the command line editing capability is given | |
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385 in this manual, @pxref{Command Line Editing}. |
| 3294 | 386 |
| 6623 | 387 @subsection Help and Documentation |
| 3294 | 388 |
| 389 Octave has an extensive help facility. The same documentation that is | |
| 390 available in printed form is also available from the Octave prompt, | |
| 391 because both forms of the documentation are created from the same input | |
| 392 file. | |
| 393 | |
| 394 In order to get good help you first need to know the name of the command | |
| 395 that you want to use. This name of the function may not always be | |
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396 obvious, but a good place to start is to type @code{help --list}. |
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397 This will show you all the operators, keywords, built-in functions, |
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398 and loadable functions available in the current session of Octave. An |
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399 alternative is to search the documentation using the @code{lookfor} |
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400 function. This function is described in @ref{Getting Help}. |
| 6620 | 401 |
| 402 Once you know the name of the function you wish to use, you can get more | |
| 403 help on the function by simply including the name as an argument to help. | |
| 404 For example, | |
| 3294 | 405 |
| 406 @example | |
| 407 help plot | |
| 408 @end example | |
| 409 | |
| 410 @noindent | |
| 411 will display the help text for the @code{plot} function. | |
| 412 | |
| 413 Octave sends output that is too long to fit on one screen through a | |
| 414 pager like @code{less} or @code{more}. Type a @key{RET} to advance one | |
| 415 line, a @key{SPC} to advance one page, and @key{q} to exit the pager. | |
| 416 | |
| 417 The part of Octave's help facility that allows you to read the complete | |
| 418 text of the printed manual from within Octave normally uses a separate | |
| 419 program called Info. When you invoke Info you will be put into a menu | |
| 420 driven program that contains the entire Octave manual. Help for using | |
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421 Info is provided in this manual, @pxref{Getting Help}. |
| 3294 | 422 |
| 4167 | 423 @node Conventions |
| 3294 | 424 @section Conventions |
| 425 | |
| 426 This section explains the notational conventions that are used in this | |
| 427 manual. You may want to skip this section and refer back to it later. | |
| 428 | |
| 429 @menu | |
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430 * Fonts:: |
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431 * Evaluation Notation:: |
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432 * Printing Notation:: |
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433 * Error Messages:: |
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434 * Format of Descriptions:: |
| 3294 | 435 @end menu |
| 436 | |
| 4167 | 437 @node Fonts |
| 3294 | 438 @subsection Fonts |
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439 @cindex documentation fonts |
| 3294 | 440 |
| 441 Examples of Octave code appear in this font or form: @code{svd (a)}. | |
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442 Names that represent variables or function arguments appear |
| 3294 | 443 in this font or form: @var{first-number}. Commands that you type at the |
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444 shell prompt appear in this font or form: @samp{octave --no-init-file}. |
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445 Commands that you type at the Octave prompt sometimes appear in this font |
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446 or form: @kbd{foo --bar --baz}. Specific keys on your keyboard appear |
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447 in this font or form: @key{ANY}. |
| 3294 | 448 |
| 4167 | 449 @node Evaluation Notation |
| 3294 | 450 @subsection Evaluation Notation |
| 451 @cindex evaluation notation | |
| 452 @cindex documentation notation | |
| 453 | |
| 454 In the examples in this manual, results from expressions that you | |
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455 evaluate are indicated with @samp{@result{}}. For example: |
| 3294 | 456 |
| 457 @example | |
| 458 @group | |
| 459 sqrt (2) | |
| 460 @result{} 1.4142 | |
| 461 @end group | |
| 462 @end example | |
| 463 | |
| 464 @noindent | |
| 465 You can read this as ``@code{sqrt (2)} evaluates to 1.4142''. | |
| 466 | |
| 467 In some cases, matrix values that are returned by expressions are | |
| 468 displayed like this | |
| 469 | |
| 470 @example | |
| 471 @group | |
| 472 [1, 2; 3, 4] == [1, 3; 2, 4] | |
| 473 @result{} [ 1, 0; 0, 1 ] | |
| 474 @end group | |
| 475 @end example | |
| 476 | |
| 477 @noindent | |
| 478 and in other cases, they are displayed like this | |
| 479 | |
| 480 @example | |
| 481 @group | |
| 482 eye (3) | |
| 483 @result{} 1 0 0 | |
| 484 0 1 0 | |
| 485 0 0 1 | |
| 486 @end group | |
| 487 @end example | |
| 488 | |
| 489 @noindent | |
| 490 in order to clearly show the structure of the result. | |
| 491 | |
| 492 Sometimes to help describe one expression, another expression is | |
| 493 shown that produces identical results. The exact equivalence of | |
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494 expressions is indicated with @samp{@equiv{}}. For example: |
| 3294 | 495 |
| 496 @example | |
| 497 @group | |
| 498 rot90 ([1, 2; 3, 4], -1) | |
| 499 @equiv{} | |
| 500 rot90 ([1, 2; 3, 4], 3) | |
| 501 @equiv{} | |
| 502 rot90 ([1, 2; 3, 4], 7) | |
| 503 @end group | |
| 504 @end example | |
| 505 | |
| 4167 | 506 @node Printing Notation |
| 3294 | 507 @subsection Printing Notation |
| 508 @cindex printing notation | |
| 509 | |
| 510 Many of the examples in this manual print text when they are | |
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511 evaluated. In this manual the printed text resulting from an example |
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512 is indicated by @samp{@print{}}. The value that is returned by |
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513 evaluating the expression is displayed with @samp{@result{}} |
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514 (@code{1} in the next example) and follows on a separate line. |
| 3294 | 515 |
| 516 @example | |
| 517 @group | |
| 518 printf ("foo %s\n", "bar") | |
| 519 @print{} foo bar | |
| 520 @result{} 1 | |
| 521 @end group | |
| 522 @end example | |
| 523 | |
| 4167 | 524 @node Error Messages |
| 3294 | 525 @subsection Error Messages |
| 526 @cindex error message notation | |
| 527 | |
| 528 Some examples signal errors. This normally displays an error message | |
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529 on your terminal. Error messages are shown on a line beginning with |
| 3294 | 530 @code{error:}. |
| 531 | |
| 532 @example | |
| 533 @group | |
| 7490 | 534 fieldnames ([1, 2; 3, 4]) |
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535 error: fieldnames: Invalid input argument |
| 3294 | 536 @end group |
| 537 @end example | |
| 538 | |
| 4167 | 539 @node Format of Descriptions |
| 3294 | 540 @subsection Format of Descriptions |
| 541 @cindex description format | |
| 542 | |
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543 Functions and commands are described in this manual in a |
| 3294 | 544 uniform format. The first line of a description contains the name of |
| 545 the item followed by its arguments, if any. | |
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546 @ifnottex |
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547 The category---function, command, or whatever---appears at the |
| 3294 | 548 beginning of the line. |
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549 @end ifnottex |
| 3294 | 550 @iftex |
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551 The category---function, command, or whatever---is printed next to the |
| 3294 | 552 right margin. |
| 553 @end iftex | |
| 554 The description follows on succeeding lines, sometimes with examples. | |
| 555 | |
| 556 @menu | |
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557 * A Sample Function Description:: |
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558 * A Sample Command Description:: |
| 3294 | 559 @end menu |
| 560 | |
| 4167 | 561 @node A Sample Function Description |
| 3294 | 562 @subsubsection A Sample Function Description |
| 563 @cindex function descriptions | |
| 564 | |
| 565 In a function description, the name of the function being described | |
| 566 appears first. It is followed on the same line by a list of parameters. | |
| 567 The names used for the parameters are also used in the body of the | |
| 568 description. | |
| 569 | |
| 570 Here is a description of an imaginary function @code{foo}: | |
| 571 | |
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572 @deftypefn {Function File} {} foo (@var{x}) |
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573 @deftypefnx {Function File} {} foo (@var{x}, @var{y}) |
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574 @deftypefnx {Function File} {} foo (@var{x}, @var{y}, @dots{}) |
| 3294 | 575 The function @code{foo} subtracts @var{x} from @var{y}, then adds the |
| 576 remaining arguments to the result. If @var{y} is not supplied, then the | |
| 577 number 19 is used by default. | |
| 578 | |
| 579 @example | |
| 580 @group | |
| 581 foo (1, [3, 5], 3, 9) | |
| 582 @result{} [ 14, 16 ] | |
| 583 foo (5) | |
| 584 @result{} 14 | |
| 585 @end group | |
| 586 @end example | |
| 587 | |
| 588 More generally, | |
| 589 | |
| 590 @example | |
| 591 @group | |
| 592 foo (@var{w}, @var{x}, @var{y}, @dots{}) | |
| 593 @equiv{} | |
| 594 @var{x} - @var{w} + @var{y} + @dots{} | |
| 595 @end group | |
| 596 @end example | |
| 597 @end deftypefn | |
| 598 | |
| 599 Any parameter whose name contains the name of a type (e.g., | |
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600 @var{integer} or @var{matrix}) is expected to be of that |
| 3294 | 601 type. Parameters named @var{object} may be of any type. Parameters |
| 602 with other sorts of names (e.g., @var{new_file}) are discussed | |
| 603 specifically in the description of the function. In some sections, | |
| 604 features common to parameters of several functions are described at the | |
| 605 beginning. | |
| 606 | |
| 607 Functions in Octave may be defined in several different ways. The | |
| 7001 | 608 category name for functions may include another name that indicates the |
| 3294 | 609 way that the function is defined. These additional tags include |
| 610 | |
| 611 @table @asis | |
| 6620 | 612 @item Function File |
| 613 @cindex function file | |
| 614 The function described is defined using Octave commands stored in a text | |
| 615 file. @xref{Function Files}. | |
| 616 | |
| 3294 | 617 @item Built-in Function |
| 618 @cindex built-in function | |
| 619 The function described is written in a language like C++, C, or Fortran, | |
| 620 and is part of the compiled Octave binary. | |
| 621 | |
| 622 @item Loadable Function | |
| 623 @cindex loadable function | |
| 624 The function described is written in a language like C++, C, or Fortran. | |
| 625 On systems that support dynamic linking of user-supplied functions, it | |
| 626 may be automatically linked while Octave is running, but only if it is | |
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627 needed. @xref{External Code Interface}. |
| 3294 | 628 |
| 629 @item Mapping Function | |
| 630 @cindex mapping function | |
| 631 The function described works element-by-element for matrix and vector | |
| 632 arguments. | |
| 633 @end table | |
| 634 | |
| 4167 | 635 @node A Sample Command Description |
| 3294 | 636 @subsubsection A Sample Command Description |
| 637 @cindex command descriptions | |
| 638 | |
| 639 Command descriptions have a format similar to function descriptions, | |
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640 except that the word `Function' is replaced by `Command'. Commands are |
| 7001 | 641 functions that may be called without surrounding their arguments in |
| 3294 | 642 parentheses. For example, here is the description for Octave's |
| 643 @code{cd} command: | |
| 644 | |
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645 @deftypefn {Command} {} cd dir |
| 11547 | 646 @deftypefnx {Command} {} chdir dir |
| 3294 | 647 Change the current working directory to @var{dir}. For example, |
| 648 @kbd{cd ~/octave} changes the current working directory to | |
| 649 @file{~/octave}. If the directory does not exist, an error message is | |
| 650 printed and the working directory is not changed. | |
| 11547 | 651 @end deftypefn |
| 3294 | 652 |