R help - Jan 2012 - Merging and subsetting with row names XXXX

Hello everyone,

I have two questions:

1)

I want to create a subset of a data frame column-wise and simultaneously
extract the row names into a "proper" variable. I tried this, but
received
an error:
>
myleft<-mydata[c(id=row.names(mydata),"workshop","gender","q1","q2")]
Error in `[.data.frame`(mydata, c(id = row.names(mydata), "workshop", 
:
  undefined columns selected
Is the following the best way to go about this:
>
myleft<-data.frame(id=row.names(mydata),mydata)[c("id","workshop","gender","q1","q2")]
> myleft
2)

Is it possible to merge data using merge() with a by variable that is the
row names? I tried this:
> both<-merge(myleft,myright,by=row.names(myleft))
Error in fix.by(by.x, x) : 'by' must specify valid
column(s)
> both
Suggestions?


Thanks!

Dan

	[[alternative HTML version deleted]]

Hi

As you did not provide any data you probably can not get canned solution
> Hello everyone,
> 
> I have two questions:
> 
> 1)
> 
> I want to create a subset of a data frame column-wise and simultaneously
> extract the row names into a "proper" variable. I tried this, but
received
> an error:
> 
> >
myleft<-mydata[c(id=row.names(mydata),"workshop","gender","q1","q2")]
> Error in `[.data.frame`(mydata, c(id = row.names(mydata),
"workshop",  :
>   undefined columns selected
> Is the following the best way to go about this:
> 
> >
> myleft<-data.frame(id=row.names(mydata),mydata)[c
>
("id","workshop","gender","q1","q2")]
> > myleft
If I understand correctly you want only some columns, all rows and make 
also new column identical with row names.

either
cbind(id=row.names(mydata),mydata[, c(2,4,5,6)])

or
data.frame(id=row.names(mydata),mydata[, c(2,4,5,6)])
 
can do it.
> 
> 2)
> 
> Is it possible to merge data using merge() with a by variable that is 
the

AFAI no.
> row names? I tried this:
> 
> > both<-merge(myleft,myright,by=row.names(myleft))
> Error in fix.by(by.x, x) : 'by' must specify valid column(s)
> > both
> Suggestions?
Regards
Petr

> 
> 
> Thanks!
> 
> Dan
> 
>    [[alternative HTML version deleted]]
> 
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