R help - Jan 2011 - filtering a dataframe with a vector of rownames

Hello,

Here's my problem. I have a large data frame and a vector with some of its
row names. I'd like to have a new data frame only with those rows that match
this vector of row names.

I tried this:

data<-cbind(c(1,2,3,4,5,6),c(2,3,4,5,6,7))
rownames(data)<-c("a", "b",
"c","d","e","f")
names.to.keep<-c("a", "c", "d")
rows.to.keep<-which(rownames(data)==names.to.keep)

But it didn't work. Any suggestions?

thanks a lot.

Jonathan.
 		 	   		  
	[[alternative HTML version deleted]]

Jonathan -
    To make your approach work, you'd need to replace =with %in%:
> rows.to.keep<-which(rownames(data) %in% names.to.keep)
[1] 1 3 4

But to answer you're original question, remember that the
point of rownames is that they can be used to index a 
data frame:
> data[rows.to.keep,]
   [,1] [,2]
a    1    2
c    3    4
d    4    5


 					- Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Fri, 14 Jan 2011, Jonathan Hughes wrote:
>
>
> Hello,
>
> Here's my problem. I have a large data frame and a vector with some of
its row names. I'd like to have a new data frame only with those rows that
match this vector of row names.
>
> I tried this:
>
> data<-cbind(c(1,2,3,4,5,6),c(2,3,4,5,6,7))
> rownames(data)<-c("a", "b",
"c","d","e","f")
> names.to.keep<-c("a", "c", "d")
> rows.to.keep<-which(rownames(data)==names.to.keep)
>
> But it didn't work. Any suggestions?
>
> thanks a lot.
>
> 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.
>

subset(data, row.names(data) %in% name.to.keep
HTH,
Anjan

On Fri, Jan 14, 2011 at 1:25 PM, Jonathan Hughes <
jonathan.hughes.10@live.com> wrote:
>
>
> Hello,
>
> Here's my problem. I have a large data frame and a vector with some of
its
> row names. I'd like to have a new data frame only with those rows that
match
> this vector of row names.
>
> I tried this:
>
> data<-cbind(c(1,2,3,4,5,6),c(2,3,4,5,6,7))
> rownames(data)<-c("a", "b",
"c","d","e","f")
> names.to.keep<-c("a", "c", "d")
> rows.to.keep<-which(rownames(data)==names.to.keep)
>
> But it didn't work. Any suggestions?
>
> thanks a lot.
>
> Jonathan.
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@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.
>


-- 
==================================anjan purkayastha, phd.
research associate
fas center for systems biology,
harvard university
52 oxford street
cambridge ma 02138
phone-703.740.6939
==================================
	[[alternative HTML version deleted]]

On 14.01.2011 19:25, Jonathan Hughes wrote:
>
>
> Hello,
>
> Here's my problem. I have a large data frame and a vector with some of
its row names. I'd like to have a new data frame only with those rows that
match this vector of row names.
>
> I tried this:
>
> data<-cbind(c(1,2,3,4,5,6),c(2,3,4,5,6,7))
> rownames(data)<-c("a", "b",
"c","d","e","f")
> names.to.keep<-c("a", "c", "d")
> rows.to.keep<-which(rownames(data)==names.to.keep)
replace the last line by

  rows.to.keep <- data[names.to.keep,]

and please read the docs on indexing.

Best,
Uwe Ligges

> But it didn't work. Any suggestions?
>
> thanks a lot.
>
> 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.