MATLAB: Selecting array column elements using a vector..

Question

Hi everyone,

I need to select elements from a 2D array. I have an index vector whose (i)'th value is the desired row to select from the array. Is there a good, simple method to do this..?

In the following code, I want to extract the following (row,column) array elements: (3,1), (2,2), (4,3), (1,4) : giving the vector: [9 11 15 13]

>> A = magic(4)

A =

    16     2     3    13
     5    11    10     8
     9     7     6    12
     4    14    15     1

>> viRow = [3 2 4 1]

viRow =

     3     2     4     1

Referring to the doc page on Matrix Indexing, I thought my solution would have been: A(viRow,:) However, this code applies the index vector to each column, which isn't what I want.

>> A(viRow,:)

ans =

     9     7     6    12
     5    11    10     8
     4    14    15     1
    16     2     3    13

Could someone please point me in the right direction?

Thanks, Brad

Answer 1

Vi=[3 2 4 1];
A=magic(4);
Index=sub2ind(size(A),Vi,1:4);
B=A(Index)