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Small tutorial for online access to Octave


More information at : Octave main page at gnu.org

First steps

You are allowed to type your formulae and calculation program in text area provided.
Try with something simple i.e. type 3/7 inside it and click "GO".

If you put ; after your commands you will not get the answer for that command. The output of the preceding command will be suppresed , try :
x = 2+3
y= x * 5;
z=x^y
you should get the result as :
octave>  x = 2+3
x = 5
octave> y= x * 5;
octave> z=x^y
z = 2.9802e+17
You are allowed to use standard math constants like pi, e, true, false, etc. in your formulaes.
If you need more decimal digits (more significancy) for the output try to put format long.
If you just need two decimal digits of your computation  put format  bank in the given text area.

Matrices and arrays

You can declare them as follows :
octave> b = [ 3; 5; 1 ]
b =

3
5
1

octave> A = [ 1, 1, 2; 3, 5, 8; 13, 21, 34 ]
A =

1 1 2
3 5 8
13 21 34

To calculate transpose of the matrix by using ' operator like A'  :
octave> A'
ans =

1 3 13
1 5 21
2 8 34

Linear equation

To solve the set of linear equations ax = b, use the left division operator, `\':

     A \ b

The code above will produce in output the solvation of the linear equation

octave> A / b
ans =

0.28571
1.20000
5.08571

Complex numbers

To specify complex constants, you can write an expression of the form
     3 + 4i
3.0 + 4.0i

0.3e1 + 40e-1i

Squares and square roots

^ is operator for calculating squares, and sqrt for calculate square root, i.e. you can use :
 sqrt (x^2 + y^2) 
to check Pitagoras theorem :)

More operators and functions

You can use C style comparison operators like ==, <, <=, <> (this is not C style operator) and symilar. Try some of them.
Also C style incremental operators are supported : ++ and --.  x++ means x=x+1
ceil (x)   returns the smallest integer not less than x.
exp (x)  - Compute the exponential of x
gcd (a1, ...) compute the greatest common divisor
log (x) - Compute the natural logarithm for each element of x
sign (x) - Compute the signum function
Trigonometry functions like cos, sin, tan, cos, acos, atan are supported.
Hyperbolic functions like tanh, cosh, sinh, atanh, asech are supported.
For multiplying two polynoms use conv (a, b) - Convolve two vectors
For deviding two polynoms use deconv (y, a) - Deconvolve two vectors
roots (v) - finds root of polynomial
polyout (c, x) - Write formatted polynomial
             c(x) = c(1) * x^n + ... + c(n) x + c(n+1)


More info

For more information about topics above and about differential equations, optimization (linear, nelinear programming), statistics, financial functions and more consult Octave manual at GNU.org