matrix extract without using for loop

I have matrix like below

A=[ 1  2  3  4  5  6  7;
    8  9 10 11 12 13 14;
   15 16 17 18 19 20 21];

start=[1 3 4];  rowSize=2;

if I use for loop,

B=zeros(3,3);
for i=1:3
 B(i,:)=A(i,start(i):start(i)+rowSize);
end

This will give

B =

       1     2     3
      10    11    12
      18    19    20

Is ther anyway I can do the same process without using the for loop?

[Oleg Komarov]

Why would you want to avoid the loop? In this case I doubt vectorization would add to the performance.

Answer 1

[Andrei Bobrov]

start=[1 3 4];
rowSize=2;
out = cell2mat(arrayfun(@(i1)A(i1,start(i1)+(0:rowSize)),(1:size(A,1))','un',0));

OR

start=[1 3 4];
rowSize=2;
n = size(A,1);
out = A(bsxfun(@plus,(bsxfun(@plus,start',0:rowSize)-1)*n,(1:n)'));

Answer 2

[Thomas]

try:

A=[ 1 2 3 4 5 6 7; 8 9 10 11 12 13 14; 15 16 17 18 19 20 21];
start=[1 3 4]; 
rowSize=2;
B=[A(start(1),start(1):start(1)+rowSize);A(2,start(2):start(2)+rowSize);A(3,start(3):start(3)+rowSize)]