Left-hand side indexing issue

Dear all,

I have a matrix A:

A = [1,2,3,4,5,6,7,8; 1,2,3,4,5,6,7,8];

I would like to change the order of matrix columns. If I try for example:

B(:,[4 3 2 1 8 7 6 5]) = A

I get:

B =
     4     3     2     1     8     7     6     5
     4     3     2     1     8     7     6     5

which is correct.

Now I try:

B(:,[3 8 2 1 6 7 5 4])=A

and I get this weird result:

B =
     4     3     1     8     7     5     6     2
     4     3     1     8     7     5     6     2

Would you have an explanation? Thank you very much!

Tobard

Answer 1

[Titus Edelhofer]

Hi,

why is it weird? You have for A:

1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8

Now you assign to the third, eighth, ... column of B the values of A, so the third column of B takes the 1, the eighth column takes the 2 and so on. Or: what did you expect?

Titus

Answer 2

[Tobard]

Oh I understand what is my problem. I was expecting B to be:

    3  8  2  1  6  7  5  4
    3  8  2  1  6  7  5  4

So I expected the written indexes to be the column indexes of A in the desired order as andrei bobrov asked. The example I chose unfortunately didn't allow me to understand this mistake.

Thank you all!

Answer 3

[Andrei Bobrov]

here all right

You want is it:

B = A(:,[3 8 2 1 6 7 5 4])