plot pdf for a large size sequence

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EEE 2014-4-4

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回答： Image Analyst 2014-4-4

I have got a sequence with size of 1 million. I want to plot a pdf for this sequence by putting same values together. Does anyone have any idea?

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Azzi Abdelmalek 2014-4-4

putting same values together: What do you mean?

EEE 2014-4-4

Thank you for your comment. For example, a sequence [1 1 1 1 1 1 2 2 2 2 3 3 3], so there are 5 1s, 4 2s and 3 3s. I want cumulate them so 1 has a magnitude of 5 and 2 has a magnitude of 4 and 3 has a magnitude of 3. Is this clear?

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Answer 1

Azzi Abdelmalek 2014-4-4

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A=[1 1 1 1 1 1 2 2 2 2 3 3 3]
[a,b,c]=unique(A)
out=accumarray(c,A')  % corresponding to a'
[a' out]

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EEE 2014-4-4

Thanks!

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Answer 2

Image Analyst 2014-4-4

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A million elements is not large at all - just a very small fraction of the number of elements in an ordinary digital image for example. It sounds like you just want the histogram. If you have all integers:

data = [1 1 1 1 1 1 2 2 2 2 3 3 3]
edges = 1 : max(data(:));
counts = histc(data, edges)
counts =
     6     4     3

Though perhaps I misunderstood because you have 5,4,3 instead of 6,4,3. Can you explain how you got the 5? Did you just ignore the first element or something???