R help - Oct 2007 - sum variable as long condition is true

Hello R

For expierienced user, the following problem will be easy to solve:

a<-c(0,1,0,1,0,2,3,4,3,2)
b<-c(3,3,3,4,4,4,7,7,7,10)
c<-data.frame(a,b)

Data Frame c contains tow colums. I would like to sum up all values in a as long
as b stays the same:

sum(a[which(b==1)])

does this, but i have to manually put in b

then i tryied st like this, but i canno't save it properly

for (i in 0:max(b)){
	i<-sum(a[which(b==i)])
}

i tried to figure out, how tapply works, but neither

thanks alot

marc
--

marcg wrote:
> Hello R
> 
> For expierienced user, the following problem will be easy to solve:
> 
> a<-c(0,1,0,1,0,2,3,4,3,2)
> b<-c(3,3,3,4,4,4,7,7,7,10)
> c<-data.frame(a,b)
> 
> Data Frame c contains tow colums. I would like to sum up all values in a as
long as b stays the same:
> 
> sum(a[which(b==1)])
> 
> does this, but i have to manually put in b
> 
> then i tryied st like this, but i canno't save it properly
> 
> for (i in 0:max(b)){
> 	i<-sum(a[which(b==i)])
> }
> 
> i tried to figure out, how tapply works, but neither
> with(c, tapply(a, list(b), sum))
 3  4  7 10
 1  3 10  2
> thanks alot
> 
> marc
> --
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
-- 
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NDRI, Inc.
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tel: (212) 845-4495 (Tu, Th)
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rowsum(c$a,c$b)

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of marcg
Sent: Tuesday, October 23, 2007 5:22 PM
To: r-help at stat.math.ethz.ch
Subject: [R] sum variable as long condition is true

Hello R

For expierienced user, the following problem will be easy to solve:

a<-c(0,1,0,1,0,2,3,4,3,2)
b<-c(3,3,3,4,4,4,7,7,7,10)
c<-data.frame(a,b)

Data Frame c contains tow colums. I would like to sum up all values in a
as long as b stays the same:

sum(a[which(b==1)])

does this, but i have to manually put in b

then i tryied st like this, but i canno't save it properly

for (i in 0:max(b)){
	i<-sum(a[which(b==i)])
}

i tried to figure out, how tapply works, but neither

thanks alot

marc
--

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

aggregate(c$a, list(b=b), sum)  

--- marcg <mdgi at gmx.ch> wrote:
> Hello R
> 
> For expierienced user, the following problem will be
> easy to solve:
> 
> a<-c(0,1,0,1,0,2,3,4,3,2)
> b<-c(3,3,3,4,4,4,7,7,7,10)
> c<-data.frame(a,b)
> 
> Data Frame c contains tow colums. I would like to
> sum up all values in a as long as b stays the same:
> 
> sum(a[which(b==1)])
> 
> does this, but i have to manually put in b
> 
> then i tryied st like this, but i canno't save it
> properly
> 
> for (i in 0:max(b)){
> 	i<-sum(a[which(b==i)])
> }
> 
> i tried to figure out, how tapply works, but neither
> 
> thanks alot
> 
> marc
> --
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained,
> reproducible code.
>