The Octave syntax is largely compatible with Matlab. The Octave interpreter can be run in GUI mode, as a console, or invoked as part of a shell script. More Octave examples can be found in the wiki.
x = -10:0.1:10; # Create an evenly-spaced vector from -10..10
y = sin (x); # y is also a vector
plot (x, y);
title ("Simple 2-D Plot");
xlabel ("x");
ylabel ("sin (x)");