# Extract area of matrices (lat, lon, data) by shapefile. "Requested array exceeds the maximum possible variable size."

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Simone A. on 31 Jan 2023
Edited: Simone A. on 31 Jan 2023
Hi all,
I've got 3 matrices, lat, lon, data (8000 X 8192 each) and one shapefile (80 X 1 struct, attached).
I need to extract only the lat, lon, data within the shapefile boundaries (and possibily with an extra buffer radius around it, let'say 1km beyond the boundary).
I tried with the other answers on the forum (i.e., https://it.mathworks.com/matlabcentral/answers/281717-extract-data-by-shapefile ) , or for instance using inpolygon, etc:
N = length(S) ;
for i = 1:N
plot(S(i).X,S(i).Y)
hold on
end
data = %MyData 8000x8192 ;
lat = %MyLat 8000x8192;
lon = %MyLon 800x8192;
[X,Y] = meshrid(lon,lat) ;
[nx,ny,d] = size(data) ;
%%Extract data
iwant = cell(d,N) ;
for i =1:d
A = data(:,:,i) ;
for j = 1:N
idx = inpolygon(X(:),Y(:),S(i).X,S(i).Y) ;
iwant{i,j} = A(idx) ;
end
end
However, when I try to make a meshgrid I belive I exceed the variable size, getting this error:
Error using repmat
Requested array exceeds the maximum possible variable size.
Error in meshgrid (line 61)
xx = repmat(xrow,size(ycol));
Is there a code you could suggest to obtain the desired result, and able to deal with the size of my matrix? The shape file covers only a tiny area (geographically speaking).

KSSV on 31 Jan 2023
Edited: KSSV on 31 Jan 2023
You need not to use meshgrid. Already your lon, lat values are in meshgrid. Remove these lines:
lat = %MyLat 8000x8192;
lon = %MyLon 800x8192;
[X,Y] = meshrid(lon,lat) ;
So your modified code should be:
N = length(S) ;
for i = 1:N
plot(S(i).X,S(i).Y)
hold on
end
data = %MyData 8000x8192 ;
lat = %MyLat 8000x8192;
lon = %MyLon 800x8192;
X = lon ;
Y = lat ;
[nx,ny,d] = size(data) ;
%%Extract data
iwant = cell(d,N) ;
for i =1:d
A = data(:,:,i) ;
for j = 1:N
idx = inpolygon(X(:),Y(:),S(i).X,S(i).Y) ;
iwant{i,j} = A(idx) ;
end
end
Simone A. on 31 Jan 2023
Edited: Simone A. on 31 Jan 2023
But the output is not a matrix, but a structure. Is there a way to obtain smaller matrices (lat, lon, data) instead? That would help a lot! thanks
Additionally, If i convert cell2mat (X = cell2mat(iwant);), I get an output where all the columns are the same:

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