How to extract values from specific coordinates

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MRobert
MRobert 2021-12-30
评论： MRobert 2022-1-1
Dear forum,
I have a plane defined by (X,Y) coordinate points on which I interpolated a scalar, as you can see in the figure attached. How may I export the scalar only for some given (X,Y) pairs? For example X = [ -0.05 0 0.05]' , Y = [ 0.01 0.025 0.05]' and I want to get the scalar in (-0.05,0.01), (0,0.025) and (0.05,0.05).
Regards,
Robert

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Matt J
Matt J 2021-12-30
编辑：Matt J 2021-12-30
You can use interp2() or griddedInterpolant().
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Matt J
Matt J 2021-12-31
编辑：Matt J 2021-12-31
Ran in:
It occurs to me that you might not know what "scalar" actually means, and this is creating confusion in the discussion. A scalar is a single number, i.e., a 1x1 matrix. Your code above makes no sense if "Initial_Scalar" is a 1x1 matrix. It also makes no sense that you would expect the output of either F(Xr,Yr) or F(X,Y) to be 1x1 matrices.
It also doesn't make sense that you used griddata if your original data was already gridded.
Here is my first impression of what I think you really want. The point is that it does give a result the same size as X and Y, and griddata is not needed.
X_FirstGrid=linspace(-0.1,0.1);
Y_FirstGrid=linspace(0,0.05);
V=X_FirstGrid.^2.*Y_FirstGrid(:); %Some made-up surface
F=griddedInterpolant({X_FirstGrid, Y_FirstGrid}, V);
X = [ -0.05 0 0.05]' ; Y = [ 0.01 0.025 0.05]';
result = F(X,Y)
result = 3×1
1.0e+-3 * 0.0450 0.0000 0.3750
MRobert
MRobert 2022-1-1
Hello,
Sorry for the way of expressing. Indeed this is what I was looking for!
Thank you,
Regards,
Robert

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