Simple Octave Operatons
malt> octave
GNU Octave, version 2.1.33 (i386-redhat-linux-gnu).
Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001 John W. Eaton.
This is free software with ABSOLUTELY NO WARRANTY.
For details, type `warranty'.
*** This is a development version of Octave. Development releases
*** are provided for people who want to help test, debug, and improve
*** Octave.
***
*** If you want a stable, well-tested version of Octave, you should be
*** using one of the stable releases (when this development release
*** was made, the latest stable version was 2.0.16).
octave:1> # A simple example of using Octave
octave:1> # Turn on the diary
octave:1> diary on
octave:2>
octave:2> # Output the value of a built-in variable
octave:2> DEFAULT_LOADPATH
DEFAULT_LOADPATH = .:/usr/libexec/octave/2.1.33/site/oct/i386-redhat-linux-gnu//:/usr/libexec/octave/site/oct/i386-redhat-linux-gnu//:/usr/share/octave/2.1.33/site/m//:/usr/share/octave/site/m//:/usr/libexec/octave/2.1.33/oct/i386-redhat-linux-gnu//:/usr/share/octave/2.1.33/m//
octave:3>
octave:3>
octave:3> # Some simple arithmetic
octave:3>
octave:3> x = 10
x = 10
octave:4> y = 4
y = 4
octave:5> x + y
ans = 14
octave:6> z = (x + y) / 2
z = 7
octave:7> disp (z)
7
octave:8> printf ("%d = %d + %d\n", z, x, y);
7 = 10 + 4
octave:9>
octave:9>
octave:9>
octave:9> # Build a row vector
octave:9>
octave:9> rv = [2, 4, 6, 7]
rv =
2 4 6 7
octave:10> # Sum all the elements
octave:10>
octave:10> sum (rv)
ans = 19
octave:11> # Transpose
octave:11> rv'
ans =
2
4
6
7
octave:12> # Product of elements
octave:12> prod (rv)
ans = 336
octave:13> # Obvious
octave:13> sort (rv)
ans =
2 4 6 7
octave:14> #Add elements
octave:14>
octave:14> rv = [rv 0 5 8 2 0]
rv =
2 4 6 7 0 5 8 2 0
octave:15> sort (rv)
ans =
0 0 2 2 4 5 6 7 8
octave:16> # find nonzero elements
octave:16> find (rv)
ans =
1 2 3 4 6 7 8
octave:17> rv ([find(rv)])
ans =
2 4 6 7 5 8 2
octave:18>
octave:18> # Create a matrix
octave:18>
octave:18> #Create a column vector
octave:18>
octave:18> cv = [5;2;0;6;9]
cv =
5
2
0
6
9
octave:19> # Simple arithmetic
octave:19> cv + 2
ans =
7
4
2
8
11
octave:20> cv * 2
ans =
10
4
0
12
18
octave:21> x ^ 2
ans = 100
octave:22> # Power function
octave:22> cv ^ 2
error: for A^b, A must be square
error: evaluating binary operator `^' near line 22, column 4
octave:22> cv .^ 2
ans =
25
4
0
36
81
octave:23> x < 4
ans = 0
octave:24> cv < 4
ans =
0
1
1
0
0
octave:25>
octave:25>
octave:25> # Create a matrix
octave:25>
octave:25> m = [1 3 5;2 4 6]
m =
1 3 5
2 4 6
octave:26> # Transpose
octave:26> m'
ans =
1 2
3 4
5 6
octave:27> m.'
ans =
1 2
3 4
5 6
octave:28> m * 2
ans =
2 6 10
4 8 12
octave:29> m ./ 2
ans =
0.50000 1.50000 2.50000
1.00000 2.00000 3.00000
octave:30> m .\ 2
ans =
2.00000 0.66667 0.40000
1.00000 0.50000 0.33333
octave:31> # Add with matrix
octave:31> m + [2 4 2]
error: operator +: nonconformant arguments (op1 is 2x3, op2 is 1x3)
error: evaluating binary operator `+' near line 31, column 3
octave:31> m + [1;2]
error: operator +: nonconformant arguments (op1 is 2x3, op2 is 2x1)
error: evaluating binary operator `+' near line 31, column 3
octave:31> m2 = [2 2 4;1 3 1]
m2 =
2 2 4
1 3 1
octave:32> # Matrix multiplication
octave:32> m * m2'
ans =
28 15
36 20
octave:33> # Element by element multiplication
octave:33> m .* m2
ans =
2 6 20
2 12 6
octave:35> # Applying functions to the matrix
octave:35> max (m)
ans =
2 4 6
octave:36> max (m')
ans =
5 6
octave:37> max (max (m))
ans = 6
octave:38> reshape (m, 6,1)
ans =
1
2
3
4
5
6
octave:39> m
m =
1 3 5
2 4 6
octave:40> prod (m)
ans =
2 12 30
octave:41> rem (m, m2)
ans =
1 1 1
0 1 0
octave:42> rem (m, 4)
ans =
1 3 1
2 0 2
octave:43> s = [5 2 1; 6 6 2; 3 3 4]
s =
5 2 1
6 6 2
3 3 4
octave:44> diag (s)
ans =
5
6
4
octave:45> inv (s)
ans =
0.33333 -0.09259 -0.03704
-0.33333 0.31481 -0.07407
0.00000 -0.16667 0.33333
octave:46> pinv (s)
ans =
3.3333e-01 -9.2593e-02 -3.7037e-02
-3.3333e-01 3.1481e-01 -7.4074e-02
-4.1660e-17 -1.6667e-01 3.3333e-01
octave:47> eig (s)
ans =
10.4051
2.0000
2.5949
octave:48> det (s)
ans = 54.000
octave:49> s * inv (s)
ans =
1.00000 -0.00000 0.00000
-0.00000 1.00000 0.00000
-0.00000 0.00000 1.00000
octave:50> rows (s)
ans = 3
octave:51> columns (s)
ans = 3
octave:52> s > 4
ans =
1 0 0
1 1 0
0 0 0
octave:53> # Special matrices
octave:53>
octave:53> eye (3,4)
ans =
1 0 0 0
0 1 0 0
0 0 1 0
octave:54> ones (2,2)
ans =
1 1
1 1
octave:55> zeros (5,1)
ans =
0
0
0
0
0
octave:56> rand (3,3)
ans =
0.021344 0.876873 0.080671
0.123355 0.996146 0.932937
0.892503 0.413795 0.701691
octave:57> sum(rem(s,s')==0)==2
ans =
0 0 0
octave:58> s (2,3)
ans = 2
octave:59> s (2,3) = 8
s =
5 2 1
6 6 8
3 3 4
octave:60> s(1:2,2)
ans =
2
6
octave:61> s(1:2,2:3)
ans =
2 1
6 8
octave:62> s(1)
error: single index only valid for row or column vector
octave:62> s(1,:)
ans =
5 2 1
octave:63> disp (pi)
3.1416
octave:64> diary off
octave:65>