thanks Michael.
I played with your suggestion to get the output in the format I wanted, and
I found the following that works fine:

sub<-d[, which(colnames(d) %in% v) ]

Aurelien

2011/12/2 R. Michael Weylandt <michael.weylandt@gmail.com> <
michael.weylandt@gmail.com>

> How about this?
>
> d[, v[v %in% colnames(d)]]
>
> Michael
>
> On Dec 2, 2011, at 12:01 PM, Aurélien PHILIPPOT <
> aurelien.philippot@gmail.com> wrote:
>
> > Hi Paul and Jim,
> > Thanks for your messages.
> >
> > I just wanted R to give me the columns of my data frame d, whose names
> > appear in v. I do not care about the names of v that are not in d. In
> > addition, every time, there will be at least one element of v that has a
> > corresponding column in d, for sure, so I know there is at least one
> match
> > between the 2.
> >
> > Initially, I  tried something in the spirit:
> > sub<- subset(d, colnames(d) %in% v)
> >
> > but I could not make it work properly.
> >
> >
> > Best,
> > Aurelien
> >
> > 2011/12/2 Paul Hiemstra <paul.hiemstra@knmi.nl>
> >
> >> On 12/02/2011 07:20 AM, Aur�lien PHILIPPOT wrote:
> >>> Dear R-users,
> >>> -I am new to R, and I am struggling with the following problem.
> >>>
> >>> -I am repeating the following  operations hundreds of times, within a
> >> loop:
> >>> I want to subset a data frame by columns. I am interested in the
> columns
> >>> names that are given by the rows of another data frame that was built
> in
> >>> parallel. The solution I have so far works well as long as the elements
> >> of
> >>> the second data frame are included in the column names of the first
> data
> >>> frame but if an element from the second object is not a column name of
> >> the
> >>> first one, then it bugs.
> >>
> >> Hi Aurelien,
> >>
> >> I would call this a feature, not a bug. I think R does what it should
> >> do, you request a non-existent column and it throws an error. What kind
> >> of behavior are you looking for instead of this error?
> >>
> >> regards,
> >> Paul
> >>
> >>>
> >>> -More concretely, I have the following data frames d and v:
> >>> yyyymmdd<-c("19720601", "19720602", "19720605")
> >>> sret.10006<-c(1,2,3)
> >>> sret.10014<-c(5,9,7)
> >>> sret.10065<-c(10,2,11)
> >>>
> >>>
> >>> d<- data.frame(yyyymmdd=yyyymmdd, sret.10006=sret.10006,
> >>> sret.10014=sret.10014, sret.10065=sret.10065)
> >>>
> >>> v<- data.frame(V1="sret.10006", V2="sret.10090")
> >>> v<- sapply(v, function(x) levels(x)[x])
> >>>
> >>> -I want to do the following subsetting:
> >>> sub<- subset(d, select=c(v))
> >>>
> >>>
> >>> and I get the following error message:
> >>> Error in `[.data.frame`(x, r, vars, drop = drop) :
> >>>  undefined columns selected
> >>>
> >>>
> >>>
> >>> Any help would be very much appreciated,
> >>>
> >>> Best,
> >>> Aurelien
> >>>
> >>>      [[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.
> >>
> >>
> >> --
> >> Paul Hiemstra, Ph.D.
> >> Global Climate Division
> >> Royal Netherlands Meteorological Institute (KNMI)
> >> Wilhelminalaan 10 | 3732 GK | De Bilt | Kamer B 3.39
> >> P.O. Box 201 | 3730 AE | De Bilt
> >> tel: +31 30 2206 494
> >>
> >> http://intamap.geo.uu.nl/~paul
> >> http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770
> >>
> >>
> >
> >    [[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.
>

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