for loop in order to put matrix elements in single row vectors

Hello,

I have a nxk (10x20) matrix called M and I am setting its rows in 1x20 vectors with

n=10;

for i=1:1:n

vector1(1,:)=M(1,:);

...

vector10(1,:)=M(10,:);

Afterwards, I do some operations with the vectors like

sum(vector1,...,vector10)

I need to form a loop that it considers the changing of n within a range, for example

2<n<40

The operation sum should be done for each n seperately,

for n=2; sum2=

. . .

for n=40; sum40=

Any help please?

Thank you very much.

Best,

Pavlos