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How to subset the matrix/array with shape file?

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Shakir Hussain
Shakir Hussain on 26 Jun 2018
Commented: Shakir Hussain on 19 Aug 2018
I have matrix of 890*751 and array 890*751*5 and I want to clip/crop/subset this matrix and array with shape file. The shape file is consist on several sub-polygon inside. Each inside sub-polygon of shape file has to clip/crop/subset separately and save with unique name. E.g, we have a shape file with 4 sub-polygon (with name (a,b,c,d) and we have to get 4 clip/crop/subset(a,b,c,d) of the matrix/array with. we can read the shape file by
area = shaperead('shapefile', 'UseGeoCoords', true);
geoshow( area , 'Facecolor', 'blue')
but no idea how to crop/clip/subset the matrix/array. The sample testmatrix, testarray and shapefile are attached here for easy to understand the question. Thank you in advance for any helpe/guide

  3 Comments

KSSV
KSSV on 26 Jun 2018
YOu need to provide the lat and lons for matrices.
Shakir Hussain
Shakir Hussain on 26 Jun 2018
Dear KSSV, the lat lon of matrix are attached here

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Accepted Answer

KSSV
KSSV on 26 Jun 2018
Edited: KSSV on 26 Jun 2018
Check this link for a similar question. You can follow the same code.
shapefile = 'shapefile.shp' ;
S = shaperead(shapefile) ;
N = length(S) ;
for i = 1:N
plot(S(i).X,S(i).Y)
hold on
end
lon = load('testlon.mat') ; lon = lon.testlon ;
lat = load('testlat.mat') ; lat = lat.testlat ;
[X,Y] = meshgrid(lon,lat) ;
data = load('testarray.mat') ; data = data.testarray ;
[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

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Shakir Hussain
Shakir Hussain on 18 Aug 2018
Error in ==> run at 18 idx = inpolygon(X(:),Y(:),S(i).X,S(i).Y) ; Here is the error I am getting from the code ( Index exceeds array bounds)
KSSV
KSSV on 18 Aug 2018
What is i? I think i is going beyond length(S).
Shakir Hussain
Shakir Hussain on 19 Aug 2018
Yes, Now it is fixed and code is working well. Last thing is how we convert the result (iwant) into 2d matrix according to the polygon extend?

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