The number of consecutive ocurrances in an array

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reham elnabawy 2017-4-30

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/338064-the-number-of-consecutive-ocurrances-in-an-array

评论： Stephen23 2017-5-1

I have an array that is shown as: a=[0,0,1,1,1,0,0,1] and I would like to get the number of consecutive ocurrances in it along with the number itself meaning that I would like the output to be b=[2,0,3,1,2,0,1,1] where 0 occurred two consecutive times, 1 occurred three consecutive times, etc. Please help me and thank you in advance.

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John Chilleri 2017-5-1

The b is a description of vector a:

Two 0s, then three 1s, then two 0s, then one 1.

Stephen23 2017-5-1

@Image Analyst: run length encoding.

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回答（1 个）

Guillaume 2017-5-1

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https://ww2.mathworks.cn/matlabcentral/answers/338064-the-number-of-consecutive-ocurrances-in-an-array#answer_265185

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This is trivially achieved with diff and find:

a = [0, 0, 1, 1, 1, 0, 0, 1];
transitions = find(diff(a));
runlengths = diff([0, transitions, numel(a)]);
runvalues = a([transitions, end]);
valuelength = reshape([runlengths; runvalues], 1, [])