function to find longest string of consecutive ones

hi all, i'm new here. i'v got some difficulties to draft a function to find longest string of consecutive ones (DNA sequence)

for ex: AAAGGTCCATTTTTTTAA

it shows TTTTTTT

Answer 1

[MaryD]

This is quick made example how it may work. Nbest tells number of letters in the longest string and Lbest tells what letters the string consists of

clear;clc;close all;
str='AAATTTTTCCCCCAATTCCC';
AGTCstr='AGTC';
Strsize=size(str);
AGTCsize=size(AGTCstr);
temp=0;
k=0;
Nbest=0;
for i=1:Strsize(2)
    for j=1:AGTCsize(2)
      h=strcmp(str(i),AGTCstr(j));
      if h==0
          continue
      end
      if h==1
          k=k+1;
           
           if strcmp(temp,str(i))==0
               if k>=Nbest
               Nbest=k;
               Lbest=temp;
              
               end
               k=0;
           end
           temp=str(i);
                      
      end
    end
end

Answer 2

[Image Analyst]

Use findgroups() and regionprops():

s = 'AAAGGTCCATTTTTTTAA' - 'A'
g = findgroups(s)
for k = 1 : max(g)
	props = regionprops(g == k, 'Area');
	largestAreas(k) = max([props.Area]);
	fprintf('The largest stretch of group %d is %d.\n', k, largestAreas(k));
end

You'll see in the command window:

The largest stretch of group 1 is 3.

The largest stretch of group 2 is 2.

The largest stretch of group 3 is 2.

The largest stretch of group 4 is 7.