summing and combining rows

Hi,
Not sure why you mentioned "+" doesn't work.
dat1<-read.table(text="
Plot??????? Elevation??????? Area??????? SizeClass??? Stems
12??????????? 1200??????????? 132.4??????? Class3??????????? 0
12??????????? 1200??????????? 132.4??????? Class4??????????? 1
17??????????? 2320??????????? 209.1??????? Class3??????????? 3
17??????????? 2320??????????? 209.1??????? Class4??????????? 5
",sep="",header=TRUE,stringsAsFactors=FALSE)

dat2<-aggregate(Stems~Plot+Elevation+Area, data=dat1,sum)
?dat3<-data.frame(dat2,SizeClass=rep("Class34",2))
?dat3<-dat3[,c(1:3,5,4)]
?dat3
#? Plot Elevation? Area SizeClass Stems
#1?? 12????? 1200 132.4?? Class34???? 1
#2?? 17????? 2320 209.1?? Class34???? 8

A.K.






----- Original Message -----
From: Christopher R. Dolanc <crdolanc at ucdavis.edu>
To: arun <smartpink111 at yahoo.com>
Cc: 
Sent: Tuesday, August 7, 2012 5:47 PM
Subject: Re: [R] summing and combining rows

Thanks for your response. The aggregate method mostly works for me, but 
I have numerous other columns that I'd like to keep in the result. So, 
if I have something like this:


Plot? ? ? ? Elevation? ? ? ? Area? ? ? ? SizeClass? ? Stems
12? ? ? ? ? ? 1200? ? ? ? ? ? 132.4? ? ? ? Class3? ? ? ? ? ? 0
12? ? ? ? ? ? 1200? ? ? ? ? ? 132.4? ? ? ? Class4? ? ? ? ? ? 1
17? ? ? ? ? ? 2320? ? ? ? ? ? 209.1? ? ? ? Class3? ? ? ? ? ? 3
17? ? ? ? ? ? 2320? ? ? ? ? ? 209.1? ? ? ? Class4? ? ? ? ? ? 5

How can I make it look like this?

Plot? ? ? ? Elevation? ? ? ? Area? ? ? ? SizeClass? ? Stems
12? ? ? ? ? ? 1200? ? ? ? ? ? 132.4? ? ? ? Class34? ? ? ?  1
17? ? ? ? ? ? 2320? ? ? ? ? ? 209.1? ? ? ? Class34? ? ? ?  8

I see something in ?aggregate about adding columns with a +, but this 
doesn't quite work for me.

Hi,

Try this:
dat1<-read.table(text="
Plot? ? SizeClass? ? Stems
12? ? ? Class3? ? ? ? ? ? 1
12? ? ? Class4? ? ? ? ? ? 3
17? ? ? Class3? ? ? ? ? ? 5
17? ? ? Class4? ? ? ? ? ? 2
",sep="",header=TRUE, stringsAsFactors=FALSE)



ddply(dat1,.(Plot), summarize, sum(Stems))

#or


dat2<-aggregate(Stems~Plot,data=dat1,sum)
?  dat3<-data.frame(dat2,SizeClass=rep("Class34",2))
?  dat3
#? Plot Stems SizeClass
#1?  12? ?  4?  Class34
#2?  17? ?  7?  Class34


A.K.

----- Original Message -----
From: Christopher R. Dolanc <crdolanc at ucdavis.edu>
To: r-help at r-project.org
Cc:
Sent: Tuesday, August 7, 2012 1:47 PM
Subject: [R] summing and combining rows

Hello,

I have a data set that needs to be combined so that rows are summed by a group based on a certain variable. I'm pretty sure rowsum() or rowsums() can do this but it's difficult for me to figure out how it will work for my data based on the examples I've read.

My data are structured like this:

Plot? ? SizeClass? ? Stems
12? ? ?  Class3? ? ? ? ? ? 1
12? ? ?  Class4? ? ? ? ? ? 3
17? ? ?  Class3? ? ? ? ? ? 5
17? ? ?  Class4? ? ? ? ? ? 2

I simply want to sum the size classes by plot and create a new data frame with a size class called "Class34" or with the SizeClass variable removed. I actually do have other size classes that I want to leave alone, but combine 3 and 4, so if I could figure out how to do this by creating a new class, that would be preferable.

I've also attached a more detailed sample of data.

Thanks,
Chris Dolanc

-- Christopher R. Dolanc
Post-doctoral Researcher
University of Montana and UC-Davis

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Christopher R. Dolanc
Post-doctoral Researcher
University of Montana and UC-Davis