Find at least 4 consecutive values less than 1 in an array

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Neha
Neha 2014-1-29
评论： Jos (10584) 2014-1-29
I have an array in which I need to find four or more consecutive values that are less than one. For example: M = [1 0 .3 .5 .2 .1 6 7 .3 .5 10 1 .8 .9 .7 .2 .1 .3]
The program should return the indexes 3-6 and 13-18.
How can I go about solving this?

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回答（6 个）

Roger Stafford
Roger Stafford 2014-1-29
编辑：Roger Stafford 2014-1-29
Here's another one-liner if you accept initial indices as an answer.
f = find(all(hankel(M(1:4),M(4:end))<1,2));
Azzi Abdelmalek
Azzi Abdelmalek 2014-1-29
编辑：Azzi Abdelmalek 2014-1-29
Edit
M= [1 0 .3 .5 .2 .1 6 7 .3 .5 10 1 .8 .9 .7 .2 .1 .3]
if diff(size(M))<0
M=M'
end
a=M<1;
b=strrep(num2str(a),' ','');
[ii,jj]=regexp(b,'1+','start','end')
d=jj-ii>=4
out=[ii;jj];
out=out(:,d)
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Azzi Abdelmalek
Azzi Abdelmalek 2014-1-29
编辑：Azzi Abdelmalek 2014-1-29
If you copy and paste the code, there is no error, unless you are using M that is not a 1xn array. What is the size of M
size(M)

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Azzi Abdelmalek
Azzi Abdelmalek 2014-1-29
编辑：Azzi Abdelmalek 2014-1-29
Edit
M= [1 0 .3 .5 .2 .1 6 7 .3 .5 10 1 .8 .9 .7 .2 .1 .3];
if diff(size(M))<0
M=M'
end
a=[0 M<1 0];
ii=strfind(a,[0 1]);
jj=strfind(a,[1 0])-1;
d=jj-ii>=4;
out=[ii;jj];
out=out(:,d)
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Azzi Abdelmalek
Azzi Abdelmalek 2014-1-29
It doesn't matter if the length changes. Maybe you are asking if the size changes, from 1xn to nx1. In this case we can edit our code. Look at edited answesrs

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José-Luis
José-Luis 2014-1-29
M = [1 0 .3 .5 .2 .1 6 7 .3 .5 10 1 .8 .9 .7 .2 .1 .3];
numVal = 4;
your_vals = conv(double(M<1),ones(1,numVal)/numVal,'valid') == 1;
start = find(diff([0 your_vals]) == 1)
finish = fliplr(numel(M) + 1 - find(diff([0 fliplr(your_vals)]) == 1))
Andrei Bobrov
Andrei Bobrov 2014-1-29
t = M<1&M>0;
t1 = [true;diff(t(:))~=0];
idx=accumarray(cumsum(t1),(1:numel(M))',[],@(x){x});
ii = idx(t(t1));
out = ii(cellfun(@numel,ii)>=4);
Jos (10584)
Jos (10584) 2014-1-29
编辑：Jos (10584) 2014-1-29
Here is a relatively simple one-liner:
M = [1 0 .3 .5 .2 .1 6 7 .3 .5 10 1 .8 .9 .7 .2 .1 .3] % example data
[startIDX, endIDX] = regexp(char((M(:).'< 1)+'0'), '1111+')

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