for loop to repeat specified number of times

I have 40448x20 matrix. I need to extract 1st 9 rows in one loop iteration, next 9 rows in second iteration and so on.and store each iteration output to perform some calculation.

Answer 1

[Alan Stevens]

If M is your 40448x20 matrix then something like

for i = 1:9:40448
    K = M(i:i+8,:);
    
    ... other calculations with K
        
end

Since 40448 is not exactly divisible by 9 this will leave a few rows of M untouched at the end. You will have to deal with them separately.

[Tuba Arif]

k is returning only last iteration of loop.

[Alan Stevens]

If you want the K matrices outside of this loop then perhaps something like:

c = 1;
K = zeros(floor(40448/9),20);
for i = 1:9:40448
    K(c,:) = M(i:i+8,:);
    c = c+1;
    ... other calculations with K
        
end

[Tuba Arif]

isn't working! it throughs following error.

Unable to perform assignment because the size of the left side is 1-by-20 and the size of the right side is 9-by-20.

[Alan Stevens]

Oh yes! I guess you'll have to do the extra calculations within the loop! At the moment I'm not sure how to save the K's individually (though why would you want to, as you have all the numbers in the large matrix anyway?).

[Alan Stevens]

You could use a structure to store the smaller matrices:

c = 1;

for i = 1:9:40448
    K(c).m = M(i:i+8,:);
    c = c+1;
    ... other calculations with K
        
end

K is now a structure

Access by K(1).m, or K(2).m etc.