Summing groups of ones

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?

[Oleg Komarov]

Can you provide an example of input and output?

[William]

This might be helpful: http://www.mathworks.com/matlabcentral/newsreader/view_thread/160813

Answer 1

[Image Analyst]

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).

[Sonia Wiemann]

This solution is just giving me one number in answer.....I have a data set that is 000001111110000001111100000011111 with much longer sections....can I get the program to feed back an answer like 5,6,6,5,6,5....counting each group separately?

[Andrei Bobrov]

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]

Sonia: See that answer in your post about that question.

Answer 2

[Rick Rosson]

   y = cumsum(x);
   d = x(2:end) - x(1:end-1);
   k = ( d == -1 );
   z = y(k);

Answer 3

[Andrei Bobrov]

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)]