Thanks so much for the tips, I was able to use both parse() and eval()... I
found eval(), quote(), bquote() easier and more flexible to use and to pass
as arguments to a function.

I can't say enough that you really made my day! :)

Thanks,
Santosh

On Tue, Dec 1, 2009 at 9:36 AM, baptiste auguie <
baptiste.auguie@googlemail.com> wrote:

> Hi,
>
> an alternative to parse() is to use quote and bquote,
>
> set.seed(123)
> d = data.frame(a=letters[1:5], b=1:10, c=sample(0:1, 10, repl=TRUE))
>
> cond1 <- quote(a=="b")
> cond2 <- quote(b < 6)
> cond3 <- bquote(.(cond1) & .(cond2))
>
> subset(d, eval(cond1))
> subset(d, eval(cond2))
> subset(d, eval(cond3))
>
> HTH,
>
> baptiste
>
>
>
> 2009/12/1 William Dunlap <wdunlap@tibco.com>:
> >> -----Original Message-----
> >> From: r-help-bounces@r-project.org
> >> [mailto:r-help-bounces@r-project.org] On Behalf Of Santosh
> >> Sent: Tuesday, December 01, 2009 7:39 AM
> >> To: r-help@r-project.org
> >> Subject: Re: [R] "subset" or "condition" as argument to a function
> >>
> >> Dear R gurus..
> >> I had tried out some suggestions sent to me privately..and
> >> unfortunately,
> >> they did not work..
> >>
> >> To use a condiition in a subset, the associated dataframe needs to be
> >> attached and detached, which I found cumbersome to use if
> >> using more than 1
> >> dataframe (with different dimensions) with same condition. I
> >> would highly
> >> appreciate your suggestions to overcome this problem.. Please
> >> see my example
> >> of usage I am trying to implement. Please note that the
> >> "cond' takes in the
> >> character instead of logical values...
> >>
> >> cond1 <- 'group==1&sales>200'
> >> cond2 <- 'group==2&sales>200'
> >> cond3 <- 'group==3&sales>200'
> >>
> >> d1 <- subset(dat,subset=cond1)
> >> plot(y~x,data=dat,subset=cond1,type='b')
> >
> > The subset argument to plot (and many similar functions)
> > must be given as a literal expression, not a string that
> > could be parsed into an expression nor the name of an object
> > containing an expression nor a function call that evaluates
> > to an expression.  This design is handy for interactive
> > use but painful in programatic use.  One way to deal with
> > it is to use do.call, which evaluates all the arguments to
> > the function and then calls the function with the arguments
> > given literally.  Replace the above plot call with
> >  do.call("plot", list(y~x,data=dat,subset=parse(text=cond1),type='b'))
> > and see if you get what you want.
> >
> > Bill Dunlap
> > Spotfire, TIBCO Software
> > wdunlap tibco.com
> >
> >> lines(y~x,data=dat,subset=cond2)
> >> points(y~x,data=dat,subset=paste(cond1,cond2,sep='&'),col='blue')
> >> points(y~x,data=d1,subset=cond3,col='red')
> >>
> >> If I try the above, I get the following error message:
> >> *Error in subset.data.frame(dat, cond) : 'subset' must
> >> evaluate to logical*
> >>
> >> If you could also suggest references implementing similar
> >> code, I would
> >> highly appreciate it.
> >> Thanks so much,
> >>
> >> Santosh
> >>
> >> On Mon, Nov 23, 2009 at 6:38 PM, Santosh
> >> <santosh2005@gmail.com> wrote:
> >>
> >> > Thanks... I would try it out..
> >> >  -santosh
> >> >
> >> >
> >> > On Sat, Nov 21, 2009 at 12:04 AM, Bernardo Rangel Tura <
> >> > tura@centroin.com.br> wrote:
> >> >
> >> >> On Fri, 2009-11-20 at 17:40 -0800, Santosh wrote:
> >> >> > Dear Rxperts!
> >> >> >
> >> >> > I was wondering if it is possible to write a function
> >> which can take in
> >> >> > argument of a subset or condition.. Of course, I am aware of the
> >> >> alternate
> >> >> > methods like coplot, par.plot, xyplot etc... I am specifically
> >> >> interested in
> >> >> > using conditions/subsets with "plot"..
> >> >> >
> >> >> > A simple fragmented example is shown here..
> >> >> >
> >> >> > pltit <- function(y,x,dat,dat1,dat2,sbst) {
> >> >> > plot(y~x, data=dat, subset=sbst)
> >> >> > lines(y~x,data=dat1, subset=subst)
> >> >> > points(y~x,data=dat2,subset=subst)
> >> >> > }
> >> >> >
> >> >> > pltit(profit,weeks,dat=zone1, sbst='group==1&sales>200')
> >> >> >
> >> >> > Could you also suggest pointers/references/examples on
> >> efficient ways to
> >> >> > plot simulated data overlaid with observed data?
> >> >> >
> >> >> > Have a good weekend!
> >> >>
> >> >>
> >> >>
> >> >
> >>
> >>       [[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.
> >>
> >
> > ______________________________________________
> > 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.
> >
>
> ______________________________________________
> 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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