Need of a nested loop:
How would we sum each individual column, rather than getting an overall sum?
Answer:
The programming technique would need a nested loop in which the outer loop is over the columns. For illustration, we will modify the earlier function to sum each column and return a row vector containing the results.
Note: The output argument will be a row vector containing similar number of columns as the input argument matrix
Also, as the function is computing a sum for each column the runsum variable should be initialized to 0 for every column. Therefore it is initialized inside of the outer loop.
>> mat = [3:5; 2 5 7]
mat =
3 4 5
2 5 7
>> matcolsum(mat)
ans =
5 9 12
Obviously, the built-in sum function in a MATLAB would accomplish similar thing.