Load data from a tab delimited file (octave sizes the array for you). The semicolon supresses the console output:
a = load sphstate.00001;
Copy just the first column into another matrix. The two arguments in the brackets are row,column ranges. E.g. (1:5,1:5) is a slice with the first five rows and first five columns.
b = a(:,1)
Plot the first two columns against each other:
plot( a(:,1), a(:,2), ‘@’)
The @ specifies point style.
Plot a 3D surface:
[rho,p] = meshgrid(0:0.05:2,0:0.05:1);
t = (1./rho) .* (1 .- (rho ./2)) .* (p .+ (2 .* (rho .** 2)));