interp2 problem: input grid is not a valid meshgrid

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Kim
Kim on 13 Jun 2014
Commented: dpb on 13 Jun 2014
I would like to interpolate, but I keep on getting the message: Error using interp2>makegriddedinterp (line 220) Input grid is not a valid MESHGRID.
Below is a simplified version of my data. Does anyone know how to solve this? Thank you!
Y=[30 29 27 20;32 31 29 22;35 34 32 25]
X=[0 2 5 10;0 2 5 10;0 2 5 10]
V=[1 2 3.5 4 ; 1.2 2.3 3.8 4.8; 1.4 2.6 4.2 5]
Yq=30
Xq=4
  1 Comment
dpb
dpb on 13 Jun 2014
Edited: dpb on 13 Jun 2014
Well, show what you did that raised the error and what you want. The round, translucent orb is somewhat murky today...
ADDENDUM
OK, I didn't look at the posted data closely enough first time -- from the doc for interp2 one finds--
... All the interpolation methods require that X and Y be monotonic and plaid (as if they were created using MESHGRID).
Your X data are monotonic ok, but they're not regular (plaid) as must be.

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Answers (1)

dpb
dpb on 13 Jun 2014
Edited: dpb on 13 Jun 2014
As noted in the comment, your data set doesn't meet the requirements of *interp2* of a uniform mesh in both directions. Use *TriScatteredInterp* instead...
>> F = TriScatteredInterp(X(:),Y(:),V(:));
>> F(Xq,Yq)
ans =
3.3444
>>
  4 Comments
dpb
dpb on 13 Jun 2014
R2012b has brung my machine to about all it can do even after adding all the memory it can hold. Since I've retired from consulting, not much incentive to spend $$ on all the things I've become accustomed to besides Matlab so I'll probably just stand pat until the machine dies. Then it'll be a hard decision...

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