Sum of nonzero vector elements

Asked by hdiba on 15 Sep 2016

Latest activity Commented on by hdiba on 15 Sep 2016

28 views (last 30 days)

Hallo everybody!

i have a vector with zeros and nonzero-entries. Now i would like to make the sum of the nonzero-elements between the zeros.example:

v= 1 2 3 0 0 0 4 5 0 6 7 0 8 9

out=6 9 13 17

in addition i would like to know the number of elements in each sum and the index of the first-sum element.

num= 3 2 2 2

indx= 1 7 10 13

can anyone help? thanks

1 Comment

José-Luis on 15 Sep 2016

Is this homework? What have you tried so far?

You could have a look at bwconncomp().

2 Answers

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Answer by Azzi Abdelmalek on 15 Sep 2016

Accepted Answer

v= [1 2 3 0 0 0 4 5 0 6 7 0 8 9]
ii=[0 v~=0 0]
idx1=strfind(ii,[0 1])
idx2=strfind(ii,[1 0])-1
out=cell2mat(arrayfun(@(x,y) [sum(v(x:y));y-x+1;x],idx1,idx2,'un',0))

1 Comment

hdiba on 15 Sep 2016

Thanks a lot !! perfect

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Answer by Andrei Bobrov on 15 Sep 2016

Edited by Andrei Bobrov on 15 Sep 2016

v= [1 2 3 0 0 0 4 5 0 6 7 0 8 9];
b = bwlabel(v(:));
[a,ii] = unique(b,'first');
indx = ii(a ~= 0);
t = b ~= 0;
num = accumarray(b(t),1);
out = accumarray(b(t),v(t));

if you not have Image Processing Toolbox then:

t = v(:) ~= 0;
p = diff([false;t]) == 1;
indx2 = find(p);
ii = cumsum(p);
num2 = accumarray(ii,t);
out2 = accumarray(ii,v(:));

You are now following this question

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