Cumulative sum with condition

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Ravi Kumar
Ravi Kumar on 22 Oct 2021
Edited: Dave B on 22 Oct 2021
I want to do cumulative sum of column 3/4 with condition in coulmn 5/6 .
example:
i.e. -0.0700+0
than -0.9800 + (-0.9800+0.4950) + (-0.9800+0.4950+0.1680)+.....so on till 0.2070
than it should start summing 3: 3.3590 + (3.3590 + 1.7470) + .....

Accepted Answer

Dave B
Dave B on 22 Oct 2021
Edited: Dave B on 22 Oct 2021
I think what you're looking for is groupsummary (or grouptransform):
x=[rand(10,1) randi(3,10,1)];
% this is the sum for groups 1,2,3
[groupsums,groups] = groupsummary(x(:,1),x(:,2),'sum')
groupsums = 3×1
0.7349 2.6445 1.5777
groups = 3×1
1 2 3
% this is what you described, the sum of the cumulative sum
[groupsums,groups]=groupsummary(x(:,1),x(:,2),@(x)sum(cumsum(x)))
groupsums = 3×1
0.8584 9.7034 2.2265
groups = 3×1
1 2 3
% here's just the cumsum:
x=sortrows(x,2); % sorting is not necessary, just makes it easier to visualize
groupcumsums=grouptransform(x(:,1),x(:,2),@(x)cumsum(x));
[x groupcumsums]
ans = 10×3
0.1235 1.0000 0.1235 0.6113 1.0000 0.7349 0.0059 2.0000 0.0059 0.8389 2.0000 0.8448 0.7340 2.0000 1.5788 0.5824 2.0000 2.1612 0.3069 2.0000 2.4682 0.1764 2.0000 2.6445 0.6488 3.0000 0.6488 0.9288 3.0000 1.5777

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