how to find the sum of multiple non zero elements in an array
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hi, i have an array that has like zero and non zero elements like eg: 0 0 0 1 1 1 0 0 0 3 3 3 0 0 0
so i want output i=3 and j=9 that is the sum of first set on nonzero elements seporate and the second seporate
1 comentario
Jan
el 4 de Jun. de 2013
Is "i" and "j" really required? Note that this might get extremely complicated, when you have 5000 such blocks and have to avoid collisions with other existing variables.
Respuesta aceptada
Jan
el 4 de Jun. de 2013
Editada: Jan
el 4 de Jun. de 2013
a = [0 0 0 1 1 1 0 0 0 3 3 3 0 0 0];
c = cumsum(a);
index = strfind([a,0] ~= 0, [true, false]);
result = [c(index(1)), diff(c(index))];
Not tested yet!
2 comentarios
Jan
el 5 de Jun. de 2013
@Mitson: Do you mean something like this:
index = strfind([0, a] ~= 0, [false, true]) + 1;
Más respuestas (3)
Roger Stafford
el 4 de Jun. de 2013
There is an ambiguity in the posing of this problem. Are the sets of nonzero numbers distinguished from one another by their values or by their contiguity? For example, if your vector were [1 3 0 3 1] do you want [2 6] (distinguished by values) as a result or [4 4] (distinguished by contiguity)? The following assumes the latter.
Let x be the row vector of your numbers.
t = [0,x,0];
c = cumsum(t);
f = find(diff(t~=0)~=0);
r = c(f(2:2:end))-c(f(1:2:end));
My apologies to you, Jan, if this seems too similar to your solution. I couldn't resist giving it.
3 comentarios
Roger Stafford
el 4 de Jun. de 2013
Editada: Roger Stafford
el 4 de Jun. de 2013
Don't you mean the former, Matt?
Matt J
el 4 de Jun. de 2013
[u,i,j]=unique([0 0 0 1 1 1 0 0 0 3 3 3 0 0 0])
result = histc(j,1:max(j)).*u
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