How do I resize a matrix in MATLAB?
Question
Suppose I had a 1-by-12 matrix and I wanted to resize it to a 4-by-3 matrix. How could I do this?
My current solution is kind of ugly:
for n = 1:(length(mat)/3)
out(n,1:3) = mat( ((n-1)*3 + 1):((n-1)*3 + 3) );
end
Is there a better way to do this?
Solution
reshape
is of course the proper solution, as stated by @gnovice.
A nice feature of reshape
is that it allows this:
A = 1:12;
B = reshape(A,4,[]);
B =
1 5 9
2 6 10
3 7 11
4 8 12
So if you don't know how many columns there will be, reshape
will compute it for you. Likewise, reshape
will fill in the number of rows, if you leave that out.
C = reshape(A,[],4)
C =
1 4 7 10
2 5 8 11
3 6 9 12
OTHER TIPS
Try the RESHAPE function:
A = (1-by-12 matrix);
B = reshape(A,4,3);
Note that the matrix B will be filled with elements from A in a columnwise fashion (i.e. columns will be filled from top to bottom, moving left to right).
Example:
>> A = 1:12;
>> B = reshape(A,4,3)
B =
1 5 9
2 6 10
3 7 11
4 8 12
to extend gnovice's solution:
If you need a different order of matrix construction, use transpose (the ' operator) or permute()
to change the dimension ordering after you have called reshape()
.