3D histogram with gnuplot or octave

Question

I would like to draw a 3D histogram (with gnuplot or octave) in order to represent my data. lets say that I have a data file in the following form:

2 3 4             


        

Answer 1

Solution using only functions available in OCTAVE, tested with octave-online

This solution generates a surface in a similar way to the internals of Matlabs hist3d function.

In brief:

• creates a surface with 4 points with the "height" of each value, which are plotted at each bin edge.
• Each is surrounded by zeros, which are also plotted at each bin edge.
• The colour is set to be based on the bin values and is applied to the 4 points and the surrounding zeros. (so that the edges and tops of the 'bars' are coloured to match the "height".)

For data given as a matrix containing bin heights (bin_values in the code):

Code

bin_values=rand(5,4); %some random data

bin_edges_x=[0:size(bin_values,2)]; 
x=kron(bin_edges_x,ones(1,5));
x=x(4:end-2);

bin_edges_y=[0:size(bin_values,1)]; 
y=kron(bin_edges_y,ones(1,5));
y=y(4:end-2);

mask_z=[0,0,0,0,0;0,1,1,0,0;0,1,1,0,0;0,0,0,0,0;0,0,0,0,0];
mask_c=ones(5);
z=kron(bin_values,mask_z);
c=kron(bin_values,mask_c);

surf(x,y,z,c)

Output