How to interpolate a set of data wher the X size is different for the Y size

Question

Robert Jones 2023-1-21

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评论： Robert Jones 2023-1-22

Hello,

I have a set of data X (size=2001,1) and Y (size=3,1). The Z matrix size is (2001,3). X and Y have uniform increments by the X size is not the same as the size of Y.

Can I use meshgrid or interp2? I tried but I got errors

for meshgrid

Error using griddata

The lengths of X and Y must match the size of Z.

for interp2

Error using griddedInterpolant

Sample points vector corresponding to grid dimension 1 must contain 3 elements.

Error in interp2>makegriddedinterp (line 226)

F = griddedInterpolant(varargin{:});

Error in interp2 (line 126)

F = makegriddedinterp({X, Y}, V, method,extrap);

Error in read_mydata (line 41)

Vq = interp2(theta,phi,co_amp_db,10,22);

Error in read_mydata (line 40)

vq = griddata(theta,phi,co_amp_db,10,22)

=======================================

Here is my code

xlx=input_data_file;
sheetname='MAIN';
addpath(pathToOptimizer)
nrow=2002;
ncol=13;
rangero=[1,1,nrow,ncol];                                                        
sheetname='Test';
[NUM,TXT,RAW]=readmycells(xlx,rangero,sheetname);
phi=NUM(1,3:4:ncol)';
theta=NUM(2:nrow,1);
nnp=size(phi);
nnt=size(theta);
np=nnp(2);
nt=nnt(1);
co_amp_db=NUM(2:nrow,2:4:ncol);
co_phase_db=NUM(2:nrow,3:4:ncol);
cx_amp_db=NUM(2:nrow,4:4:ncol);
cx_phase_db=NUM(2:nrow,5:4:ncol);
vq = griddata(theta,phi,co_amp_db,10,22);
Vq = interp2(theta,phi,co_amp_db,10,22);

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Answer 1

dpb 2023-1-21

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https://ww2.mathworks.cn/matlabcentral/answers/1898260-how-to-interpolate-a-set-of-data-wher-the-x-size-is-different-for-the-y-size#answer_1153575

在 MATLAB Online 中打开

x=1:10;y=1:3; % coarse spacing

z=rand(numel(x),numel(y));

surf(y,x.',z)

hold on

Z=interp2(y,x.',z,1:0.5:3,[1:0.5:10].'); % increase spacing by half...

surf(1:0.5:3,[1:0.5:10].',Z); % plot on top...

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VBBV 2023-1-22

移动：VBBV 2023-1-22

Check also scatteredInterpolant or griddedInterpolant

Robert Jones 2023-1-22

Thank you

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Answer 2

Jonas 2023-1-21

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1898260-how-to-interpolate-a-set-of-data-wher-the-x-size-is-different-for-the-y-size#answer_1153585

在 MATLAB Online 中打开

you can usw meshgrid to prepare your xq and yq:

Y=9:13;X=1:2:5;Z=rand(5,3);
[xq,yq]=meshgrid(1:0.5:5,9:0.5:13);
interp2(X,Y,Z,xq,yq)

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Robert Jones 2023-1-22

Thank you

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