Octave

Plotting 3D
x=1:0.2:5; % x=[1,5]
y=1:0.2:5; % y=[1,5]
[X,Y] = meshgrid(x,y);
Z=((X).^2+(Y)-11).^2+((Y).^2+(X)-7).^2;
surf(X,Y,Z)
plot(x,sin(x)) 2D plot
x=sin(t); y=cos(t),z=t; plot3(x,y,z)


Basics

exp(1) e
log is natural log
j is unit complex

variables
who lists variables
clear variablename
help format
format long
size(X) matrix size
save name.txt save variables, eg see sminf.txt
load name.txt load variables