MATLAB: Size problems with interp2

Question

Hello,

I am working with data that I retrieved from remote sensing and would like to increase the spatial resolution of my data (to work alongside other data of different resolution).

My data matrix is a 2D matrix, where each x and y location yields a data value.

For example, I would like to increase the resolution of my matrix from 38×90 to 500×1000.

Here is what I tried:

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[a b] = size(SST); %where SST is my 2D matrix containing data values…so then a would be 38 and b would be 90

x = 1:a; %This would serve as the x vector for SST data, x would be 1:38

y = 1:b; %This would serve as the y vector for SST data, y would be 1:90

XI = linspace(1,38,500); %This is the x resolution that I want YI = linspace(1,90,1000); %This is the y resolution that I want

[x y] = meshgrid(x,y); %create vector arrays [XI YI] = meshgrid(XI,YI); %create vector arrays

SST_hiRes = interp2(x,y,SST,XI,YI);

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So basically I receive the following error:

"??? Error using ==> interp2 at 145 Matrices X and Y must be the same size as Z."

I am confused because I retrieved the size of these vectors from the "Z" vector directly…..any thoughts? I don't have the image toolbox unfortunately or I would use imresize.

Thanks for any input!

—Jimmy

Answer 1

The fix

[x y] = meshgrid(y,x); %create vector arrays 
[XI YI] = meshgrid(YI,XI); %create vector arrays

You have x and y swapped, hence each is the transpose of the matrix you expect. You're confusing matrix notation (row,col) with cartesian coordinates (x,y). Also look at ndgrid for another solution/explanation.

And an FYI: You don't want to increase the resolution, you want to increase the sampling density.