Question

I’m new to Octave/Matlab and I want to plot a 3D-Graph.

I was able to do so using a predefined formula, like this:

x=1:.1:5;
y=1:.1:5;
[xx,yy] = meshgrid(x,y);
z = sin(xx)+sin(yy);
mesh(x,y,z);

But now the question is how to do the same getting the data from a CSV (for example). I know I can use the function csvread, but the big question is how to format the CSV to contain such data.

An example of doing the same graph above but this time grabbing the data from Excel/CSV would be appreciated. Thanks!

Answer 1

Done! I was finally able to do it!

Here’s how I did it:

1) I’ve created a file in Excel with the X values in the cells A2:A42, and the Y values in the cells B1:AP1 (so you form a rectangle).

2) Then in the cells in the middle I put the formula I want (ie =sin(A$2)+sin($B1))

3) Saved the file as CSV (but separated by spaces!) and manually edited it to look this way (the way QtOctave opens matrix files, in Matlab it might be different). For example (note the extra space before each column):

# Created by Octave 3.2.4, Thu Jan 12 19:32:05 2012 ART <diego@notebook2>
# name: z
# type: matrix
# rows: 3
# columns: 3
 1 2 3
 4 5 6
 7 8 9

(if you’re not sure how to do it, do what I did: create a simple matrix and export it to see how the exported file looks like!)

4) Octave has a function under Data -> Load matrix from file, which loads that kind of files. Or actually running this command (varname is the name of the resulting variable):

load("-text", "file-where-the-data-is", "varname")

5) Create the graph (ex is the name of the matrix I’ve just imported):

x=1:.1:5;
y=1:.1:5;
mesh(x,y,ex)