How to interpolate only on a certain direction?

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Alessandro Longo 2018-1-10

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评论： Matt J 2018-1-11

Hello, I have a series of matrix H of dimensions: 2x2x2049, defined for 2049 values of the frequency, from 0 to 3200 Hz. I would interpolate H so that I will have a series of matrix of dimensions 2x2x100000 for 100000 values of the frequency, from 5 to 50 Hz. How can I do this?

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Adam 2018-1-10

在 MATLAB Online 中打开

doc interp3

should work for this, provided you give it the same input and output grids for the first two dimensions.

Alessandro Longo 2018-1-10

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It does not work. I tried in this way:

 [xx,yy,zz] = meshgrid(1:2,1:2,f_swept);
 Htrue_interp = interp3(Htrue,xx,yy,zz,'spline');

where Htrue has dimension 2x2x2049 and f_swept is my long vector

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Answer 1

Matt J 2018-1-10

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https://ww2.mathworks.cn/matlabcentral/answers/376484-how-to-interpolate-only-on-a-certain-direction#answer_299490

编辑：Matt J 2018-1-10

在 MATLAB Online 中打开

Hr=reshape(  permute(H,[3,1,2]) , [],4 );  %convert to 2D array
     tmp=interp1(...,Hr,...);  %interpolate the columns
Hnew= reshape( ipermute(tmp,[3,1,2])   ,[2,2,100000] );  %convert back to 3D

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Matt J 2018-1-11

Yes it does...

Matt J 2018-1-11

在 MATLAB Online 中打开

Take this H as a simpler example

I will upsample it by a factor 2 by interpolation:

tmp=interp1(Hr,linspace(1,3,5)); 
Hnew= reshape( ipermute(tmp,[3,1,2])   ,[2,2,5] );

The result:

        Hnew(:,:,1) =
           1     1
           1     1
      Hnew(:,:,2) =
          1.5000    1.5000
          1.5000    1.5000
      Hnew(:,:,3) =
           2     2
           2     2
      Hnew(:,:,4) =
          2.5000    2.5000
          2.5000    2.5000
      Hnew(:,:,5) =
           3     3
           3     3