matlab get data from a matrix with data row and column indeces stored in arrays

Question

given the data matrix and indeces arrays for rows and columns

data=reshape(1:9,3,3)
row_index=[1,2,3];
column_index=[1,2,2];

I can get result=[1,5,6] by

for i =1:length(row_index)
   result(i)=data(row_index(i),column_index(i));
end

How to vectorize the loop?

P0W · Accepted Answer · 2015-10-05 04:53:16Z

3

Like this : ( using sub2ind )

indices = sub2ind( size(data), row_index, column_index );

Then,

result = data(indices)

answered Oct 5, 2015 at 4:53

P0W

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1 Comment

Thanks! I am wondering if there is any more direct way without converting the indeces.

Chenming Zhang · Accepted Answer · 2015-10-05 04:57:00Z

1

I also find a indirect way without using.

data(column_index*size(data,2)+row_index)

answered Oct 5, 2015 at 4:57

Chenming Zhang

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That should be column_index*size(data,1) instead.