Using a matrix as pairs of indexes of another matrix

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bbb_bbb
bbb_bbb 2019-7-4
编辑： Stephen23 2019-7-4
For instance:
x=[
1 2 3 4 5 6 7 8 9
10 20 30 40 50 60 70 80 90
100 200 300 400 500 600 700 800 900];
% idx are coordinates (row,col) of x array
idx=[1 3
2 5
3 8];
for i=1:size(idx,1) % cycle through pairs of idx
y(i)=x(idx(i,1),idx(i,2));
end
y
y =
3 50 800
How can this be done without a loop?

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Stephen23
Stephen23 2019-7-4
编辑：Stephen23 2019-7-4
"How can this be done without a loop?"
Using sub2ind, which converts to linear indices:
>> ind = sub2ind(size(x),idx(:,1),idx(:,2));
>> x(ind)
ans =
3
50
800

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