indexing

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

[Sven]

Select the code in your post and hit the "code" button to make it easier to read.

One problem we will all have is that your first statement:

a = [ q1 q2 q3 q4]

is not valid MATLAB code, so I don't quite understand what you're trying to do... can you clarify?

[Fangjun Jiang]

What does b have anything to do with this?

[deji]

the elements in a are to replace the elements in b

[Dr. Seis]

Ah, then use my last suggestion if you are using the elements in b for indexing.

Answer 1

[Dr. Seis]

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);

[bym]

yes but the OP said q1 =1...etc, in which case

a(b) == b

I don't get the question

[Dr. Seis]

Yeah, I changed it just to demonstrate that the elements in a do not necessarily need to be 1:4, but the indexing needs to be 1:length(a) in order to do any rearranging they may want to do. I, too, do not understand fully... just a few guesses.