Version 1:

for ii = 1:size(a,1)
for jj = 1:size(a,2)
if a(ii,jj) > 5
a(ii,jj) = sqrt(a(ii,jj));
end
end
end

Takes the square root of all elements in an array whose value is greater than 5. Much faster to use the vectorized approach…

Version 2:

b = a > 5;
a(b) = sqrt(a(b));

Cool.