Thread Subject: Finding the longest length of zero's...

 Subject: Finding the longest length of zero's... From: D Date: 16 Jun, 2010 22:37:04 Message: 1 of 5 Hello, I have a huge single column set of data, and within this are intervals of zero's, with each interval a different length. I used find(A==0) , and it returns a vector of the locations of all zero's. I am ultimately interested in finding the starting and stopping indices of the longest sized interval of zero's. Can anyone provide tips on how to approach this? Thank you!
 Subject: Finding the longest length of zero's... From: ImageAnalyst Date: 16 Jun, 2010 22:46:45 Message: 2 of 5 Do you have the Image Processing Toolbox? Is so, it's trivial. Just call bwlabel and regionprops then pull out the biggest object. It doesn't matter that it's a 1D "image" instead of a 2D image.
 Subject: Finding the longest length of zero's... From: Matt Fig Date: 16 Jun, 2010 23:24:22 Message: 3 of 5 ImageAnalyst wrote in message <2b1bac7a-a751-4341-b025-2e251f6bbdb7@z25g2000vbk.googlegroups.com>... > Do you have the Image Processing Toolbox? Is so, it's trivial. Just > call bwlabel and regionprops then pull out the biggest object. It > doesn't matter that it's a 1D "image" instead of a 2D image. If not, you can use your logical result this way: B = A==0; st = findstr(B.',[0 1])+1; % If A is a column vector. The starting points ed = findstr(B.',[1 0]); % The ending points. % Now, assuming you take care of any boundary problems (I leave to you).... [idx,idx] = max(ed-st); idx = st(idx)
 Subject: Finding the longest length of zero's... From: Roger Stafford Date: 17 Jun, 2010 00:13:03 Message: 4 of 5 "D " wrote in message ... > Hello, > > I have a huge single column set of data, and within this are intervals of zero's, with each interval a different length. > > I used find(A==0) , and it returns a vector of the locations of all zero's. I am ultimately interested in finding the starting and stopping indices of the longest sized interval of zero's. > > Can anyone provide tips on how to approach this? > > Thank you! - - - - - - - - -   You can also do it this way. Let d be the column vector of data.  t = diff([false;d==0;false]);  p = find(t==1);  q = find(t==-1);  [maxlen,ix] = max(q-p);  first = p(ix);  last = q(ix)-1; maxlen is the length of the longest consecutive series of zeros, first is the index of its beginning, and last is the index of its end. Roger Stafford
 Subject: Finding the longest length of zero's... From: D Date: 17 Jun, 2010 13:48:04 Message: 5 of 5 "Roger Stafford" wrote in message ... > "D " wrote in message ... > > Hello, > > > > I have a huge single column set of data, and within this are intervals of zero's, with each interval a different length. > > > > I used find(A==0) , and it returns a vector of the locations of all zero's. I am ultimately interested in finding the starting and stopping indices of the longest sized interval of zero's. > > > > Can anyone provide tips on how to approach this? > > > > Thank you! > - - - - - - - - - > You can also do it this way. Let d be the column vector of data. > > t = diff([false;d==0;false]); > p = find(t==1); > q = find(t==-1); > [maxlen,ix] = max(q-p); > first = p(ix); > last = q(ix)-1; > > maxlen is the length of the longest consecutive series of zeros, first is the index of its beginning, and last is the index of its end. > > Roger Stafford Thank you all!

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