How to get the starting and ending index of repeated numbers in an array?
14 views (last 30 days)
Show older comments
Hi MY array is =[2 2 1 2 3 2 2 2 2 2 3 5 6 7 7 7 7 6 5]
I am trying to find the starting and index index of repeated numbers in my array
for example,
for number 2, i expect startingindex=1 and endingindex=2 as it is repeated and also startingindex=6th and endingindex=10.
for number 7, i expect startingindex=14 and endingindex=17
I have been trying using find so far but in vain
0 Comments
Accepted Answer
Jan
on 22 Jun 2015
X = [2 2 1 2 3 2 2 2 2 2 3 5 6 7 7 7 7 6 5];
[B, N, Ind] = RunLength(X);
Ind = [Ind, length(X)+1];
Multiple = find(N > 1);
Start = Ind(Multiple);
Stop = Ind(Multiple + 1) - 1;
4 Comments
Azzi Abdelmalek
on 22 Jun 2015
As indicated in the above answer, you can get RunLength function in this link http://www.mathworks.com/matlabcentral/fileexchange/41813-runlength
More Answers (3)
Ingrid
on 22 Jun 2015
try using the diff function before calling find
4 Comments
Stephen23
on 22 Jun 2015
Edited: Stephen23
on 22 Jun 2015
@yashvin: notice that Ingrid mentioned two functions: diff and find. You only tried the first function, but you missed the find.
>> V = [2 2 1 2 3 2 2 2 2 2 3 5 6 7 7 7 7 6 5];
>> X = diff(V)~=0;
>> B = find([true,X]) % begin of each group
B =
1 3 4 5 6 11 12 13 14 18 19
>> E = find([X,true]) % end of each group
E =
2 3 4 5 10 11 12 13 17 18 19
>> D = 1+E-B % the length of each group
D =
2 1 1 1 5 1 1 1 4 1 1
Use logical indexing if you only want the groups with more than one element:
>> Y = D>1;
>> B(Y)
ans =
1 6 14
>> E(Y)
ans =
2 10 17
Andrei Bobrov
on 22 Jun 2015
Edited: Andrei Bobrov
on 22 Jun 2015
A=[2 2 1 2 3 2 2 2 2 2 3 5 6 7 7 7 7 6 5];
ii = [0, diff(A(:)')==0,0];
i1 = strfind(ii,[0 1]);
i2 = strfind(ii,[1 0]);
out = [A(i1)',i1(:),i2(:)];
Azzi Abdelmalek
on 22 Jun 2015
Edited: Azzi Abdelmalek
on 22 Jun 2015
A=[2 2 1 2 3 2 2 2 2 2 3 5 6 7 7 7 7 6 5];
d1=~diff(A).*(1:numel(A)-1);
idx1=d1.*[1 ~d1(1:end-1)];
idx2=circshift(d1.*[~d1(2:end) 1],[0 1]);
ii1=~~idx1;
out=[A(ii1);idx1(ii1) ;idx2(~~idx2)+1];
0 Comments
See Also
Categories
Find more on String Parsing in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!