Forming 25 portfolios in a double sort

Hello everyone, i've got the following problem. I want to create 25 portfolios sorted by two variables. So at the end i should sort one variable at the quintiles and the other variable at the quintiles which will give me 25 portfolios if I combine them. I have a solution for this, but my loops work too long (over 2 hours). Here is my first and my second loop out of an overall of 6 loops in overall.

Loop 1 for a quintile sort for the first variable

% 5 portfolios sorted for size

s1 = NaN(size(NSI));

s2 = NaN(size(NSI));

s3 = NaN(size(NSI));

s4 = NaN(size(NSI));

s5 = NaN(size(NSI));

u = 1;

 for m=1:12:589;
    n=min(594, m + 12 - 1);
    for i=1:size(NSI,2)
        if me(u,i) <= prctile(me(u,:),20,2);
            s1(m:n,i) = 1;
        elseif me(u,i) > prctile(me(u,:),20,2) & me(u,i) <= prctile(me(u,:),40,2);
            s2(m:n,i) = 1;
        elseif me(u,i) > prctile(me(u,:),40,2) & me(u,i) <= prctile(me(u,:),60,2);
            s3(m:n,i) = 1;
        elseif me(u,i) > prctile(me(u,:),60,2) & me(u,i) <= prctile(me(u,:),80,2);
            s4(m:n,i) = 1;
        elseif me(u,i) > prctile(me(u,:),80,2);
            s5(m:n,i) = 1;
        end
    end
    u = u + 12;
end

Loop 2 where I take the first portfolio of the first variable

% 5 portfolios sorted for book-to market for the smallest size portfolio

s1b1 = NaN(size(NSI));

s1b2 = NaN(size(NSI));

s1b3 = NaN(size(NSI));

s1b4 = NaN(size(NSI));

s1b5 = NaN(size(NSI));

u = 1;

 for m=1:12:589;
    n=min(594, m + 12 - 1);
    for i=1:size(NSI,2)
        if beme(u,i) <= prctile(beme(u,:),20,2);
            s1b1(m:n,i) = s1(m:n,i);
        elseif beme(u,i) > prctile(beme(u,:),20,2) & beme(u,i) <= prctile(beme(u,:),40,2);
            s1b2(m:n,i) = s1(m:n,i);
        elseif beme(u,i) > prctile(beme(u,:),40,2) & beme(u,i) <= prctile(beme(u,:),60,2);
            s1b3(m:n,i) = s1(m:n,i);
        elseif beme(u,i) > prctile(beme(u,:),60,2) & beme(u,i) <= prctile(beme(u,:),80,2);
            s1b4(m:n,i) = s1(m:n,i);
        elseif beme(u,i) > prctile(beme(u,:),80,2);
            s1b5(m:n,i) = s1(m:n,i);
        end
    end
    u = u + 12;
end

to be continued for the other 4 portfolios.

Is there a smarter way to get the 25 portfolios?. Thanks in advance.

[Sascha Winter]

The size of the matrices is 594 x 15727.