## I have matrix A, how can I add a row in matrix A with others rows of matrix A ?

on 29 May 2013

### Matt Kindig (view profile)

I have matrix A, how can I add a row in matrix A with others rows of matrix A ?
For example:
a = ones (220,220);
b = a(:,1)+a(:,11)+a(:,21)+ a(:,31)+a(:,41)+a(:,51)+a(:,61)+a(:,71)+a(:,81)+a(:,91);
I would like to obtain sum of row as b. The problem is the matrix I'm working on is thousands, is there a more easy way to do this? a certain function maybe that only needs me to specify the column number. Thank you!

### Matt Kindig (view profile)

on 29 May 2013

b = sum(a(:,1:10:91),2)

Firzi Mukhri

### Firzi Mukhri (view profile)

on 29 May 2013
it works! but what is the number 2 represent?
Matt Kindig

### Matt Kindig (view profile)

on 29 May 2013
2 is the dimension over which the summing is performed. Dimensions are ordered in the same order that they are returned from the size() function, i.e. dimension=1 is sum down the rows, dimension=2 is sum down the columns, dimension=3 is sum across dimension 3 ("planes"), etc.