Error checking in a matrix

I have the following code:

 [r , c] = size(m);

 if any(m(end,:)==-1)
     m(m<0) = 0;
 else
    for a=r-1:-1:1
        for b=1:c
            if m(a,b)==-1
                m(a,b)=m(a+1,b);
             end
        end
    end
 end

The code is checking if a matrix contains -1 in the last row. I have a couple of question regarding this code.It Works fine when checking from the last row to check for -1. If the is a -1 it replaces them all with zeros. If there are no -1 in the last row it locates the -1 and replace them with the value from the row that comes before. How do i do the opposite ? Check if the first row contains -1, and if so replace them with zeros. And if not then takes the value from the NeXT line and replace the -1 with that ?

Thanks a lot

Answer 1

[Geoff Hayes]

Carsten - just do something similar to what you have already, but opposite.

 [r, c] = size(m);
 if ~isempty(find(m(1,:)==-1))
     m(m==-1) = 0;
 else
    for a=2:1:r
        % get all indices of row a that correspond to elements
        % of negative one
        idcs = find(m(a,:)==-1);

        if ~isempty(idcs)
            m(a,idcs) = m(a-1,idcs);
        end
    end
 end

Note how find is used to return the indices of the elements in the row that are negative one.

Try the above and see what happens!

[Carsten]

Thank you so much for your help.