计算连续数字岛的长度和频率

Question

我有一个 1 和 0 的序列，我想计算连续 1 的孤岛出现的频率。

鉴于： S = [1 1 0 0 1 1 1 0 1 0 0 1 0 0 0 1 1 0 0 1 0 0 1 1 0 1]

通过计算连续岛屿的数量，我的意思是： R = [4 3 1] …因为有四个单字，三个双字和一个三字。

因此乘以岛屿的长度 [1 2 3]。

[4 3 1] * [1 2 3]’ = 13

对应sum(S)，因为有十三个

我希望将解决方案矢量化而不是循环一些东西。

我想到了类似的东西： R = histcounts(diff( [0 (find( ~ (S > 0) ) ) numel(S)+1] ))

但是这个结果没有多大意义。它计算了太多的三胞胎。我在互联网上找到的所有代码都围绕 diff([0 something numel(S)]) 但问题总是略有不同，对我没有真正帮助

感谢任何建议！

Answer 1

下面应该做的。希望评论清楚。

S = [1 1 0 0 1 1 1 0 1 0 0 1 0 0 0 1 1 0 0 1 0 0 1 1 0 1];
% use diff to find the rising and falling edges, padding the start and end with 0
edges = diff([0,S,0]); 
% get a list of the rising edges
rising = find(edges==1);
% and falling edges
falling = find(edges==-1);
% and thereby get the lengths of all the runs
SRuns = falling - rising;
% The longest run
maxRun = max(SRuns);
% Finally make a histogram, putting the bin centres 
R = hist(SRuns,1:maxRun);

Answer 2

您也可以通过以下方式获得相同的结果：

x = find(S==1)-(1:sum(S)) %give a specific value to each group of 1
h = histc(x,x)            %compute the length of each group, you can also use histc(x,unique(x))
r = histc(h,1:max(h))     %count the occurence of each length

结果：

r = 
 4,3,1

计算连续数字岛的长度和频率

Count length and frequency of island of consecutive numbers

binary

matlab

counting