[R] matching identical row names
John Kane
jrkrideau at yahoo.ca
Sun Apr 16 17:29:03 CEST 2006
Dear Dr. Fox
Your reply to Sirinivas Iyyar was most helpful to me. I am trying to collapse some categories of a data.frame in a similar way.
I have a data frame in the form below
Prog Sub.Program Job V1 V2 V3
1 Alpha A 1 2 3
2 Alpha B 2 3 1
2 Gamma B 1 3 3
2 Alpha A 3 4 1
2 Gamma B 2 2 3
1 Alpha A 2 2 2
What I want is to sum the values of VI, V2 and V3 and end up with a new data.frame that would look like
Prog Subprog Job Sum(V1) Sum(V2), Sum(V3)
1 Alpha A 3 4 5
2 Alpha A 3 4 1
2 Gamma B 3 5 6
I thought that I could use by() to create a vector for each of V1:V3 but I cannot see any way to capture the values.
temp1 <- by(Data[,4] simply gives me the complete output.
An example of what I have done is
-------------------------------------------------------------
Prog <- 1, 2, 2, 2,2,1,
Sub.Program <- c("Alpha", "Alpha", "Gamma", "Alpha", "Gamma", "Alpha" )
Job <- c("A", "B", "B", "A", "B", "A")
V1 <- c(1,2, 1,3,2,2)
V2 <- c(2, 3, 3, 4, 2, 2)
V3 <- c(3, 1 , 3, 1, 3,2
Mydata <- data.frame(cbind( Prog, Sub.Program, Job, V1, V2, V3)
by(MyData[,4],list(Sub.Program=Sub.Program, Job=Job), sum)
----------------------------------------------------------------
I also get the expected <NA. for cells that do not exist. Is there any way to set them to "0" in the operation?
Any help would be greatly appreciated.
Thanks
John
----- Original Message ----
From: John Fox <jfox at mcmaster.ca>
To: Srinivas Iyyer <srini_iyyer_bio at yahoo.com>
Cc: r-help at stat.math.ethz.ch
Sent: Saturday, April 15, 2006 9:35:46 AM
Subject: Re: [R] matching identical row names
Dear Srinivas,
Your data are likely in a data frame rather than a matrix (since the columns
are heterogeneous), and name is a variable, not the row names of the data
frame.
There are several ways to do what you want; one simple way, assuming that
the data are in a data frame named Data, is
by(Data[,2:5], Data$name, mean)
If you want the result in the form of a matrix, then you could do
aggregate(Data[,2:5], list(Data$name), mean)
I hope this helps,
John
--------------------------------
John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox
--------------------------------
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Srinivas Iyyer
> Sent: Friday, April 14, 2006 11:58 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] matching identical row names
>
> dear group,
>
> i have a sample matrix
> name v1 v2 v3 v4
> cat 10 11 12 15
> dog 3 12 10 14
> cat 9 12 12 15
> cat 5 12 10 11
> dog 12 113 123 31
> ...
>
>
> since cat is repeated 3 times, I want a mean value for it.
> Like wise for every element of the name column.
> cat v1 = mean(c(10,9,5))
> cat v3 = mean(c(11,12,13))
> ..etc.
>
> name v1 v2 v3 v4
> cat 8 11.6 11.3 13.6
> dog 7.5 62.5 66.5 22.5
>
> could any one help me in solving this mystery. thank you.
>
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