MATLAB Answers


Is the 3D griddata example correct?

Asked by Matt
on 1 May 2013

I'm trying to get my head around griddata so that I can plot an intensity as the colour on a 3D surface (a hemisphere). When I start with the example on the Mathworks website "Interpolate 3-D data set over over a grid in the x-y plane" I get the same error as I do in my own code. The code copied from the Mathworks website is as follows:

x = 2*rand(5000,1)-1; 
y = 2*rand(5000,1)-1; 
z = 2*rand(5000,1)-1;
v = x.^2 + y.^2 + z.^2;
d = -0.8:0.05:0.8;
[xq,yq,zq] = meshgrid(d,d,0);
vq = griddata(x,y,z,v,xq,yq,zq);
set(gca,'XTick',[-1 -0.5 0 0.5 1]);
set(gca,'YTick',[-1 -0.5 0 0.5 1]);

The subsequent error is as follows:

Error using griddata (line 51)
XI and YI must be the same size or vectors of different orientations.
Error in griddatatest (line 11)
vq = griddata(x,y,z,v,xq,yq,zq);

I presume I have copied and pasted it correctly from Mathworks Central?! I thought it would be a good place to start for my own code...


Well I just tried it with version (R2010a) on my mac OS X and it doesn't work. I wonder if they updated griddata in the newer versions. I will try another computer on campus.

This is really frustrating because the gridddata command seems to be the easiest way to to this. I have tried for about 8 hours now. I am just trying to plot 4 different planes of data. I have come really close using the surfc command but this does not interpolate. I also want to draw contours on each of the planes.

if true
  close all
hold on
hold on
hold on
caxis([1 4.667])
xlim([2 110])
ylim([-110 0])
zlim([-18 0])

They did some pretty significant updates to the internals of griddata over the years, I can't remember exactly what release though. I think it does explain what you're seeing; there is likely a way to make in work in R2010 if needed, but the old version isn't as robust as the new one so it would require some fiddling around with the various griddata options.

Ya I checked it on one of the newer university computers with the 2012 release and it worked fine. After analyzing this script in more detail some it wasn't exactly what I wanted to do anyways.

Thanks for the speedy reply!

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