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Summing groups of ones

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Sonia Wiemann
Sonia Wiemann 2012-4-24
If I have a list of ones and zeros....the ones are clustered together in groups....how can I ask the program to sum the ones within their groups?
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Oleg Komarov
Oleg Komarov 2012-4-24
Can you provide an example of input and output?
William
William 2012-4-24
This might be helpful: http://www.mathworks.com/matlabcentral/newsreader/view_thread/160813

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采纳的回答

Image Analyst
Image Analyst 2012-4-24
Just call regionprops (if you have the image Processing Toolbox):
numberOfOnesPerGroup = regionprops(yourArray, 'area');
One line and you're done. This will get you the area (number of touching elements) for each group (elements that all touch each other).
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Andrei Bobrov
Andrei Bobrov 2012-4-25
numberOfOnesPerGroup = regionprops(~~yourArray(:), 'Area','PixelIdxList' )
numberOfZerosPerGroup = regionprops(~yourArray(:), 'Area','PixelIdxList' );
ons = [ones(numel(numberOfOnesPerGroup),1), cat(1,numberOfOnesPerGroup.('Area'))]
out = zeros(numel(numberOfOnesPerGroup)+numel(numberOfZerosPerGroup),2);
if numberOfOnesPerGroup(1).PixelIdxList(1) < numberOfZerosPerGroup(1).PixelIdxList(1)
out(1:2:end,:) = ons;
out(2:2:end,2) = cat(1,numberOfZerosPerGroup.('Area'));
else
out(2:2:end,:) = ons;
out(1:2:end,2) = cat(1,numberOfZerosPerGroup.('Area'));
end
Image Analyst
Image Analyst 2012-4-25
Sonia: See that answer in your post about that question.

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更多回答（2 个）

Rick Rosson
Rick Rosson 2012-4-24
y = cumsum(x);
d = x(2:end) - x(1:end-1);
k = ( d == -1 );
z = y(k);
Andrei Bobrov
Andrei Bobrov 2012-4-24
x1 = [~x(1) x(:)' ~x(end)]
groupones = diff([strfind(x1,[0 1]);strfind(x1,[1 0])]);
variant
x1 = x(:);
k = find([true;diff(x1)~=0]);
out = [x1(k) diff([k,[k(2:end);numel(x1)+1]],1,2)]

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