R help - Nov 2013 - averaging rows on a data.frame according to a factor

Dear all,

I apologize for the newbie question, but I'm stuck.

I have a data frame in the following form:

dat<-as.data.frame(cbind(c("a","a","a","b","b"),
c(1,2,3,3,2),c(4,3,5,4,4)))

I need a way to generate a new dataframe with the average for each factor.
The result should look like:

res<-as.data.frame(cbind(c("a","b"), c(2,2.5),c(4,4)))

Any help would be greatly appreciated.

Jonathan

	[[alternative HTML version deleted]]

On Nov 22, 2013, at 1:43 PM, john d wrote:
> Dear all,
> 
> I apologize for the newbie question, but I'm stuck.
> 
> I have a data frame in the following form:
> 
>
dat<-as.data.frame(cbind(c("a","a","a","b","b"),
c(1,2,3,3,2),c(4,3,5,4,4)))
> 
> I need a way to generate a new dataframe with the average for each factor.
> The result should look like:
Well, using the data,frame(cbind(...)) will ensure that you will NOT get
factors, since cbind creates a matrix and that structure will not hold factors.
> 
> res<-as.data.frame(cbind(c("a","b"),
c(2,2.5),c(4,4)))
Ouch.


Look at ?tapply or ?aggregate.

Perhaps:

dat<-data.frame(facts=
c("a","a","a","b","b"),
nums1=c(1,2,3,3,2),nums2=c(4,3,5,4,4))

aggregate(dat[-1], dat[1], mean)


> Any help would be greatly appreciated.
> 
> Jonathan
> 
> 	[[alternative HTML version deleted]]
Newbie or not, you should still read the Posting Guide.
> 
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
-- 

David Winsemius
Alameda, CA, USA

Hello,

Try the following.

aggregate(cbind(V2, V3) ~ V1, dat, FUN = mean)


Hope this helps,

Rui Barradas

Em 22-11-2013 21:43, john d escreveu:
> Dear all,
>
> I apologize for the newbie question, but I'm stuck.
>
> I have a data frame in the following form:
>
>
dat<-as.data.frame(cbind(c("a","a","a","b","b"),
c(1,2,3,3,2),c(4,3,5,4,4)))
>
> I need a way to generate a new dataframe with the average for each factor.
> The result should look like:
>
> res<-as.data.frame(cbind(c("a","b"),
c(2,2.5),c(4,4)))
>
> Any help would be greatly appreciated.
>
> Jonathan
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>

Hi,


dat<-as.data.frame(cbind(c("a","a","a","b","b"),
c(1,2,3,3,2),c(4,3,5,4,4)))
?str(dat)
#'data.frame':??? 5 obs. of? 3 variables:
# $ V1: Factor w/ 2 levels "a","b": 1 1 1 2 2
# $ V2: Factor w/ 3 levels "1","2","3": 1 2 3 3 2
# $ V3: Factor w/ 3 levels "3","4","5": 2 1 3 2 2

#better way would be
dat<-data.frame(V1=c("a","a","a","b","b"),
V2=c(1,2,3,3,2),V3=c(4,3,5,4,4))
?str(dat)
#'data.frame':??? 5 obs. of? 3 variables:
# $ V1: Factor w/ 2 levels "a","b": 1 1 1 2 2
# $ V2: num? 1 2 3 3 2
# $ V3: num? 4 3 5 4 4

library(plyr)
?ddply(dat,.(V1),colwise(mean))

#or
?aggregate(.~V1,data=dat,mean)

A.K.

On Friday, November 22, 2013 5:45 PM, john d <dobzhanski at gmail.com>
wrote:
Dear all,

I apologize for the newbie question, but I'm stuck.

I have a data frame in the following form:

dat<-as.data.frame(cbind(c("a","a","a","b","b"),
c(1,2,3,3,2),c(4,3,5,4,4)))

I need a way to generate a new dataframe with the average for each factor.
The result should look like:

res<-as.data.frame(cbind(c("a","b"), c(2,2.5),c(4,4)))

Any help would be greatly appreciated.

Jonathan

??? [[alternative HTML version deleted]]

______________________________________________
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.