Efficient way of performing operation on array after performing cumsum

Hi,

I am fairly new to MatLab and I would like to perform the following without using a for loop. I have a matrix A to which I have applied cumsum to create another matrix B, whose row elements are the sum of the previous ones in A.

The subsequent operation I would like to perform is to divide all the elements in the same column by the index of that column. For instance, I would like to divide column 1 by 1, column 2 by 2, and column 3 by 3, and so one. In the example below, matrix B is

B = [ 1 3 6

4 9 15

7 15 24 ]

while C would be

C = [1/1 3/2 6/3

4/1 9 /2 15/3

7/1 15/2 24/3 ]

= [1.0000 1.5000 2.0000

4.0000 4.5000 5.0000

7.0000 7.5000 8.0000]

Is there any efficient way to do this without using a for loop? I thought about using arrayfun or cellfun but I have no idea of how. My initial code is below

%Example of what I want to achieve

A = [1 2 3; 4 5 6; 7 8 9];
B = cumsum(A,2);
% The operation I would like to perform
for i=1:size(B,2)
    C(:,i)= B(:,i)/i;
end

Answer 1

[Stephen23]

A = [1,2,3;4,5,6;7,8,9];
B = cumsum(A,2);
C = B./(1:3)

C = 3×3

1.0000 1.5000 2.0000 4.0000 4.5000 5.0000 7.0000 7.5000 8.0000

[Valentina Baccetti]

Thanks! This works perfectly

Answer 2

[David Goodmanson]

Hi Valentina,

A = [1 2 3; 4 5 6; 7 8 9];
B = cumsum(A,2);
C = (1:3).\B

This gives the result that you show in your question.

[Valentina Baccetti]

Thanks! This works too