You are asking to extract all columns of multiple rows, so you are usually going to get out a something-by-2 matrix (since yearnflow{1,1} is 17532 x 2). You then ask for the max() of that. By default max() runs down the columns, so you would produce a 1 x 2 output, the max of each column. You then tried to store those two max values into a single location.
Corrected, with some minor optimization:
yf = yearnflow{1,1};
for R = 1:48
Qmax(R,:)=max(yf(RowID(R,2):RowID(R,3),:), 1);
end
This will produce Qmax as a 48 x 2 array.
If you want the max independent of the column, then you can use max(Qmax,2) after the above.
The ",1" on the max() is a good practice to account for the possibility that at some point only one row of data might be fetched from yearnflow. With only one row of data, it would look to MATLAB like a row vector instead of a pair of column vectors, so it would produce a single output instead of the expected 2. The ",1" tells MATLAB not to guess about which dimension to take the max() over, to always take the max() along the first dimension even if there is only one row.
