[R] Conditional cumulative sum

[Pete Brecknock]

Axel Urbiz wrote
> 
> Dear List,
> 
> I'll appreciate your help on this. I'm trying to create a variable as in
> "cumsum_y.cond1" below, which should compute the cumulative sum of "y"
> conditional on the value of cond==1.
> 
> set.seed(1)
> d <- data.frame(y= sample(c(0,1), 10, replace= T),
>                 cond= sample(c(0,1), 10, replace= T))
> 
> 
>    y cond  cumsum_y.cond1
>  1  0    0     0
>  2  0    0     0
>  3  1    1     1
>  4  1    0     1
>  5  0    1     1
>  6  1    0     1
>  7  1    1     2
>  8  1    1     3
>  9  1    0     3
> 10 0    1     3
> 
> Thank you.
> 
> Regards,
> Axel.
> 
> 	[[alternative HTML version deleted]]
> 
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> 


is this what you are looking for ...

set.seed(1)
d <- data.frame(y= sample(c(0,1), 10, replace= T),
                cond= sample(c(0,1), 10, replace= T)) 

d$cumsum_y.cond1 = cumsum(d$y & d$cond)

# Output
   y cond cumsum_y.cond1
1  0    0              0
2  0    0              0
3  1    1              1
4  1    0              1
5  0    1              1
6  1    0              1
7  1    1              2
8  1    1              3
9  1    0              3
10 0    1              3

HTH

Pete

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