CODEWITHSUNDEEP
arraysmatlabindexing
zeycus
zeycus

Reputation: 890

Fancy array access in Matlab

In Python numpy it is possible to use arrays of indexes, as in (taken from the tutorial):

data = array([[ 0,  1,  2,  3],
              [ 4,  5,  6,  7],
              [ 8,  9, 10, 11]])
i = array( [ [0,1],         # indices for the first dim of data
             [1,2] ] )
j = array( [ [2,1],         # indices for the second dim
             [3,3] ] )

Now, the invocation

data[i,j]

returns the array

array([[ 2,  5],
       [ 7, 11]])

How can I get the same in Matlab?

Upvotes: 1

Views: 285

Answers (1)

Dan
Dan

Reputation: 45752

I think you will have to use linear indexing which you'll get from the sub2ind function like this:

ind = sub2ind(size(data), I,J)

example:

data =[ 0,  1,  2,  3
        4,  5,  6,  7
        8,  9, 10, 11]

i = [0,1;
     1,2];

j = [2,1;
     3,3]

ind = sub2ind(size(data), i+1,j+1);
data(ind)

ans =

     2     5
     7    11

notice that I went i+1 and j+1, this is because unlike Python which starts indexing at 0, Matlab starts indexing from 1.

Upvotes: 3

Related Questions