Divide an array in areas based on its values

2013 5 28
3 个回答
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0 个投票

Suppose that I want find the edges of ones and of not ones such that I can divide an in areas the array. Suppose the array is as the example below:
a=[1 1 1 1 1 1 12 10 1 1 1 1 1 11 12 1 1 1 2 3]
a(1:6) -->area1 of ones
a(7:8) -->area1 of not ones
a(9:a13) -->area2 of ones
a(14:15)-->area2 of not ones
a(16:19)-->area3 of ones
a(20) -->area3 of not ones
and so on..

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 采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-5-28

0 个投票

a=[1 1 1 1 1 1 12 10 1 1 1 1 1 11 12 1 1 1 2 3 ]
idx=find(a==1)
e=[diff(idx) 100]
f=find(e~=1)
ff=idx(f)
ii1=[idx(1) idx(f(1:end-1)+1)]
ii2=idx(f)
idx=find(a~=1)
e=[diff(idx) 100]
f=find(e~=1)
ff=idx(f)
jj1=[idx(1) idx(f(1:end-1)+1)]
jj2=idx(f)
for k=1:numel(ii1)
area1(k)={ii1(k):ii2(k)};
area0(k)={jj1(k):jj2(k)};
end

更多回答（2 个）

Andrei Bobrov
Andrei Bobrov 2013-5-28

0 个投票

a=[1 1 1 1 1 1 12 10 1 1 1 1 1 11 12 1 1 1 2 3 ];
a1 = a == 1;
ii = [true, diff(a1)~=0];
idx = cumsum(ii);
out = accumarray(idx(:),a(:),[],@(x){x});

0 个投票

I amazed by the simplicity of the codes both of you provided. Although I have some difficulty to understand them they solve my problem.
I would be grateful if yo provided some explanation Thank you very much.

3 个评论
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Image Analyst
Image Analyst 2013-5-28
编辑：Image Analyst 2013-5-28
Please transfer this "Answer" to the other "Answer" (the one you thought you were responding to) as a comment. No one knows if you're talking to Azzi, whose answer you accepted, or Andrei, who has the shorter answer. Though I do agree with you that any compact, cryptic code could be helped with explanation/comments.
This answer is common for both of the answers that I got above considering the level of my knowledge in matlab. Therefore this answer corresponds to Azzi's and Andrei's answer and this the reason that I posted as an answer and not as a comment. I would accept both answers if this was possible. I accepted Azzi's because it is easier to comprehend.
Andrei Bobrov
Andrei Bobrov 2013-5-29
Please read the description of the three functions in the MATLAB documentation: diff, cumsum, accumarray.

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