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How to subset the matrix/array with shape file?

Asked by Shakir Hussain on 26 Jun 2018
Latest activity Commented on by Shakir Hussain on 19 Aug 2018
Accepted Answer by KSSV
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
on 26 Jun 2018
YOu need to provide the lat and lons for matrices.
Dear KSSV, the lat lon of matrix are attached here
KSSV
on 26 Jun 2018
aaah...got it....

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1 Answer

Answer by KSSV
on 26 Jun 2018
Edited by KSSV
on 26 Jun 2018
 Accepted Answer

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

  9 Comments

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
on 18 Aug 2018
What is i? I think i is going beyond length(S).
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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