Finding sequences of consecutive 1s

I need to make a function to find longest string of consecutive ones. I have code but it will record the longest string regardless of whether or not its a 1 or 0.

 % code
function output=longest_one(n)
n=str2num(n);
size_n=size(n);
size_n=size_n(2);
lenmax = 1;
len = 1;
for i = 2:size_n
   if n(i) == n(i-1) 
      len = len+1;
   else
         if len >= lenmax
            lenmax = len;
         end
         len=1;
   end

end output=lenmax end

Any ideas on how to just get the longest string of ones?

Answer 1

[Roger Stafford]

Assume 'n' is a row vector.

   f = find(diff([false,n==1,false])~=0);
   [m,ix] = max(f(2:2:end)-f(1:2:end-1));

The value of 'm' is the longest string's length, and it starts at f(2*ix-1) in 'n'.

[EFB]

Brilliant!

Answer 2

[Walter Roberson]

hint: strfind(AVector, [0 1]) tells you something about when you have a 0 followed by a 1

Answer 3

[Jan]

With FEX: RunLength without a conversion to numbers:

[b, n] = RunLength(n);
output = max(n(b == '1'));