MATLAB: Indexing

Question

hi,

how do i replace all the members of an array with with anoda set of arrays.. for example

a = [ q1 q2 q3 q4]
b = [1 2 3 4 2 4 3 1 2 1 3 4 3 2 1 2 3 4 1 3 2 4]

how do i replace the members of a with where q1=1, q2=2, q3=3 and q4=4 pls i will appreciate any help i can get for this.

thanks in advance

Answer 1

Are you trying to create a row vector with all the different combinations of q1, q2, q3, and q4?

If so:

q1=11; q2=22; q3=33; q4=44;
a = [q1 q2 q3 q4];
b = reshape(a(perms(1:length(a)))',[1,numel(perms(1:length(a)))]);

If you would rather have a matrix of the different combinations, then:

b = a(perms(1:length(a)));

Or, if the order of b is really as you describe above, then use b as indices to a:

b = [1 2 3 4 2 4 3 1 2 1 3 4 3 2 1 2 3 4 1 3 2 4];
c = a(b);