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How to show surface plot of 2D data?

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Steven
Steven on 10 Dec 2019
Commented: Star Strider on 10 Dec 2019
Hi.
I have a set of data points, C at each x and y (for many cases). In 2D, the plot looks simply like this:
So this is a sample plot for one x. There are similar plots for other x values as well.
What I want is some kind of surface plot. How can I get it? I tried to use surf and contour, but they need their z to be a matrix, not an array.
For instance, the data looks like this:
% set1
x = [1 1 1 1];
y = [1 3 5 16];
C = [100 400 200 500];
% set2
x = [2 2 2 2];
y = [4 7 8 13];
C = [200 500 700 100];
Thank you

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Accepted Answer

Star Strider
Star Strider on 10 Dec 2019
Try this (with your own vectors):
x = rand(10,1); % Create Data
y = rand(10,1); % Create Data
z = rand(10,1); % Create Data
[X,Y] = ndgrid(sort(x), sort(y)); % Create Interpolation Grids
Z = griddata(x, y, z, X, Y); % Interpolate ‘z’
figure
surf(X, Y, Z)
hold on
stem3(x, y, z, 'filled')
hold off
grid on
Experiment to get different results.

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Star Strider
Star Strider on 10 Dec 2019
I was not expecting that possibility.
Try this:
% set1
x1 = [1 1 1 1];
y1 = [1 3 5 16];
C1 = [100 400 200 500];
% set2
x2 = [2 2 2 2];
y2 = [4 7 8 13];
C2 = [200 500 700 100];
xm = [x1; x2];
ym = [y1; y2];
Cm = [C2; C2];
figure
surf(xm, ym, Cm)
grid on
Extend it for more vectors. Note that they all must have the same column sizes for this to work (that is, they all need to be row vectors with the same number of columns).
Steven
Steven on 10 Dec 2019
Unfortuantely some of them are not of the same size, but some of them are! But it works for those that are though :)
P.S., I edited the original post to include the data.
Thanks again
Star Strider
Star Strider on 10 Dec 2019
As always, my pleasure!
You can make them all the same size with the interp1 or interp2 functions. It is slightly more work, however you can then use all your data.
For example, to extend ‘x1’, ‘y1’, and ‘C1’ to each have a length of 7:
x1i = x1(1)*ones(1,7);
y1i = interp1((1:numel(x1)), y1, linspace(1, numel(x1), numel(x1i)));
C1i = interp1((1:numel(x1)), C1, linspace(1, numel(x1), numel(x1i)));
You could probably create a function to do this.

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