How do I merge two columns in a Matrix in Matlab?

I have a n x (n+1) matrix and I want to add the row elements of only the third and second column in order to arrive to a n x n matrix. Something like:

1 2 3;
4 5 6;
7 8 9

and end up with:

1  5;
4 11;
7 17

Thanks for the help!

Answer 1

[Star Strider]

Use the sum function:

A = [1 2 3;
    4 5 6;
    7 8 9];

B = [A(:,1) sum(A(:,2:3),2)]

B =
     1     5
     4    11
     7    17

[Jose Coronado]

Thank you!

What if I have n columns before the ones that I want to add? or m columns after the ones i want to add?

[Star Strider]

My pleasure!

Select the columns to exclude before and after, and sum the ones you want. For example, if ‘A’ has 10 columns and you want to sum 5, 6 and 7, this would work:

B = [A(:,1:4)  sum(A(:,5:7),2)  A(:,8:10)]

Remember to use the square brackets to concatenate the elements of ‘A’ to create ‘B’.