Finding sum of a Matrix
We may use a single colon as an index into a matrix selects all the elements of the array and arranges them (in column order) into a single column vector, Like :
Example
>> A = [1,2,3; 4,5,6; 7,8,9]
A =
1 2 3
4 5 6
7 8 9
>> A(:)
ans =
1
4
7
2
5
8
3
6
9
Same colon used to find the sum of whole matrix as :
>> sum(A(:))
ans =
45
We may find sum of Individual columns as :
>> A = [1,2,3; 4,5,6; 7,8,9]
A =
1 2 3
4 5 6
7 8 9
>> sum(A)
ans =
12 15 18
