how to write this without loop

hi! i wrote this in matlab:

 %
r is a mtrix of the size(25*30000)
for l=1:30000
    for k=2:25
       d(k,l)=r(k,l)-r(k-1,l);
        if d(k,l)<-109
          r(k,l)=r(k,l)+300;
            elseif  d(k,l)>180
                   r(k,l)=r(k,l)-300;   
        end
    end
end

how could write this with minimal loops?

thank you

Answer 1

[Jan]

d        = [zeros(1, 30000); diff(r)];
index    = (d < -109);
r(index) = r(index) + 300;
index    = (d > 180);
r(index) = r(index) - 300;

Or:

d     = [zeros(1, 30000); diff(r)];
shift = zeros(size(r));
shift(d < -109) =  300;
shift(d >  180) = -300;
r     = r + shift;

[Rica]

this is really professional :-). how to get this level?

thanks

[Rica]

there is a proble with usin diff.in may loop i use the actual value to make the difference

 %
 d(k,l)=r(k,l)-r(k-1,l);
 with the actual value of *d* means the corrected value with the if statement:

 %
 if d(k,l)<-109
          r(k,l)=r(k,l)+300;
            elseif  d(k,l)>180
                   r(k,l)=r(k,l)-300;

thank you

Answer 2

[Walter Roberson]

You can start with diff(r), and then use logical indexing.