Obtaining the values within the boundary of my map

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Benyamin Nemati
Benyamin Nemati 2020-10-14
编辑： Benyamin Nemati 2020-10-27
Hello everyone,
I have some plots that they're from a 180*360*12 matrix with a code like this:
for i = 1:12
load coast
figure(i)
hold on
imagesc(lambda-180,phi,EWT(:,:,i));
plot(long,lat,'k');
end
B_1 = shaperead('Aqueduct_river_basins_TIGRIS & EUPHRATES.shp'); %one of the shape files that ive loaded on my map
mapshow(B_1,'facecolor','none');
you can see the boundaries on the map,the north africa and middle east region, now my question is: how could i derive EWT values within these boundaries, i want the average values on these areas at the end.
thanks for your considerations.
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Benyamin Nemati
Benyamin Nemati 2020-10-15
how can i use this function on my Z values (EWT(:,:,i)) as xq and yq ?
by considering my code, what is your suggestion?

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KSSV
KSSV 2020-10-15
Something like this:
[m,n,p] = size(EWT) ;
[X,Y] = meshgrid(lambda-180,phi) ;
B_1 = shaperead('Aqueduct_river_basins_TIGRIS & EUPHRATES.shp'); %one of the shape files that ive loaded on my map
N = length(B-1.X) ; % this should have different regions
iwant = cell(N,1) ;
for i = 1:N
% Get the indices insdie this polygon
idx = inpolygon(X,Y,B_1(i).X,B_i(i).Y) ;
% Get the mean of these points
thesum = 0 ;
for j = 1:p
T = EWT(:,:,i) ;
thesum = thesum+T(idx) ;
end
iwant{i} = thesum/p ;
end
The above code gives you inside the polygon points as scattered points. If you want grid, pick the chunk, use inpoltgon and make the outside indices data to NaN.

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