# Sum of nonzero vector elements

38 views (last 30 days)
hdiba on 15 Sep 2016
Commented: hdiba on 15 Sep 2016
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
José-Luis on 15 Sep 2016
Is this homework? What have you tried so far?
You could have a look at bwconncomp().

Azzi Abdelmalek on 15 Sep 2016
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))
hdiba on 15 Sep 2016
Thanks a lot !! perfect

Andrei Bobrov on 15 Sep 2016
Edited: 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(:));

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