summing up array element
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Hello,
I am new to programming, I have an array like p = [3 6 2 5];
I need c = [3 9 11 16]; First element in the array is as it is, when it goes to next element it has to sum the previous element.
Regards, SBN
Answers (4)
Andrew Reibold
on 25 Jul 2013
Edited: Andrew Reibold
on 25 Jul 2013
Here is your solution in a really easy loop.
p = [3 6 2 5]; %Can have as many numbers as you want
for n = 2:length(p) %n can be whatever counter you want.
p(n) = p(n)+p(n-1); %semi-colon suppresses output
end
-Andrew
Iain
on 25 Jul 2013
Edited: Iain
on 25 Jul 2013
for i = 1:numel(p)
c(i) = sum(p(1:i));
end
Or
so_far = 0;
for i = 1:numel(p)
so_far = so_far + p(i);
c(i) = so_far;
end
or
for i = 1:numel(p)
s = 0;
for j = 1:i
s = s+ p(j);
end
c(i) = s;
end
1 Comment
Jan
on 25 Jul 2013
These are inefficient solutions, because the complete sum is calculated in each iteration. While this might not matter for 4 elements, the runtime will grow rapidly for longer data.
It is more efficient to re-use the sum for the elements 1 to i, when the sum until the i+1.th element is obtained. See Andrews answer.
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