Sum of nonzero vector elements

hdiba (view profile)

on 15 Sep 2016
Latest activity Commented on by hdiba

hdiba (view profile)

on 15 Sep 2016
Accepted Answer by Azzi Abdelmalek

Azzi Abdelmalek (view profile)

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

José-Luis (view profile)

on 15 Sep 2016
Is this homework? What have you tried so far?
You could have a look at bwconncomp().

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Answer by Azzi Abdelmalek

Azzi Abdelmalek (view profile)

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

hdiba (view profile)

on 15 Sep 2016
Thanks a lot !! perfect

Answer by Andrei Bobrov

Andrei Bobrov (view profile)

on 15 Sep 2016
Edited by Andrei Bobrov

Andrei Bobrov (view profile)

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(:));