The syntax is:
reshapedMatrix = reshape(key, desiredRows, desiredColumns);
If either desiredRows or desiredColumns is just empty brackets [] then it takes the one that is there and figures out what the other one should be for you, as a convenience so that you don't have to do the math yourself.
For example, since you input 2 for desiredRows, then if you use [] for desiredColumns, it will compute desiredColumns for you like this:
desiredColumns = numel(key) / 2;
It's a nice convenience, you just have to make sure that you'll have a square matrix (no ragged last row or column just partially filled with numbers. In other you must have numel(key) be a multiple of desiredRows (2 in your example). So
key = 1:6
rk = reshape(key, 2, [])
works:
key =
1 2 3 4 5 6
rk =
1 3 5
2 4 6
while
key = rand(1, 5);
reshapedMatrix = reshape(key, 2, []);
doesn't work because 5 is not a multiple of 2 and you can't have a matrix with the first two columns having 2 rows and the rightmost column having only one row. No "ragged edges" allowed.
key =
1 2 3 4 5 6
rk =
1 3 5
2 4 Can't have nothing in the lower right corner
