Swapping a range of points in a matrix

I'm trying to swap rows 6 to 10 in column 1 and rows 1 to 5 in column 2 of my matrix for a task in my computing class. So far this is the best I can manage but something is going wrong, presumably with the square brackets:

r1=zeros(5,6)
r1(2:2:30,1)=1:1:15
r1([1:5,6:10],[2,1])=r1([6:10,1:5],[1,2])

Any help would be much appreciated

[dpb]

Matlab doesn't treat arrays of indices as you're trying to use them; see what the expression returns to understand what you're getting (might want to do it for a smaller range first to get fewer values to look at and clarify what's happening).

To do multiple locations like this you'd need to use linear addressing and compute that location from subscripts via the ind2sub|sub2ind pair or write the column indices a single values in separate expressions.

As it is coursework, will leave as the above hints for further exploration... :)

Answer 1

[Roger Stafford]

Suppose your matrix is called ‘M’.

   T = M(6:10,1);
   M(6:10,1) = M(1:5,2);
   M(1:5,2) = T;

Answer 2

[Roger Stafford]

If you prefer one-liners, try this, (again calling your matrix M):

   M([6:10,(1:5)+size(M,1)]) = M([(1:5)+size(M,1),6:10]);