cs345-streams4

# cs345-streams4 - Stream Clustering Extension of DGIM to...

This preview shows pages 1–7. Sign up to view the full content.

1 Stream Clustering Extension of DGIM to More  Complex Problems

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 Clustering a Stream Assume points enter in a stream. Maintain a sliding window of points. Queries ask for clusters of points within  some suffix of the window. Important issue : where are the cluster  centroids?
3 BDMO Approach BDMO = Babcock, Datar, Motwani,  O’Callaghan. –means based. Can use less than O( N  ) space for  windows of size  N . Generalizes trick of DGIM: buckets of  increasing “weight.”

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
4 Recall DGIM Maintains a sequence of buckets B 1 , B 2 Buckets have timestamps (most recent  stream element in bucket). Sizes of buckets nondecreasing. In DGIM size = power of 2. Either 1 or 2 of each size.
5 Alternative Combining Rule Instead of “combine the 2 nd  and 3 rd  of  any one size” we could say: “Combine B i+1  and B i  if size(B i+1   B i ) <  size(B i-1    B i-2   …   B 1 ).” If B i+1 , B i , and B i-1  are the same size,  inequality must hold (almost). If B i-1  is smaller, it cannot hold.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
6 Buckets for Clustering In place of “size” (number of 1’s) we use  (an approximation to) the sum of the  distances from all points to the centroid  of their cluster.
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern