R help - Jun 2004 - subset and lme

I'm puzzled by the following problem, which appears when 
attempting to run an analysis on part of a dataset:

If I try:

  csubset <- dat$Diagnosis==0
  cont <- lme(fixed=cform,
                   random = ~1|StudyName,
                      data=dat,subset=csubset,na.action=na.omit)

Then I get:

Error in eval(expr, envir, enclos) : Object "csubset" not found

But if I do instead:

  cdat <- dat[dat$Diagnosis==0,]
  cont <- lme(fixed=cform,
                   random = ~1|StudyName,
                      data=cdat,na.action=na.omit)

Then everything is fine.

I'm puzzled that the object can't be found.  Maybe I'm 
overlooking something obvious?

Best,

Todd Ogden

Hoi Todd,

--On woensdag 16 juni 2004 10:18 -0400 Todd Ogden <to166 at columbia.edu> 
wrote:
> I'm puzzled by the following problem, which appears when
> attempting to run an analysis on part of a dataset:
>
> If I try:
>
>   csubset <- dat$Diagnosis==0
>
This just creates a vector of booleans that indicate (the row numbers) for 
which positions in dat Diagnosis==0.
>
>   cdat <- dat[dat$Diagnosis==0,]
>
This OTOH, uses the above vector to index the rows of dat, indeed selecting 
those rows from dat that have Diagnosis==0. This is assigned to cdat. You 
could have done

cdat <- dat[csubset,]

as well


HTH



-- 
Paul Lemmens
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Todd Ogden wrote:
> I'm puzzled by the following problem, which appears when 
> attempting to run an analysis on part of a dataset:
> 
> If I try:
> 
>   csubset <- dat$Diagnosis==0
>   cont <- lme(fixed=cform,
>                    random = ~1|StudyName,
>                       data=dat,subset=csubset,na.action=na.omit)
> 
> Then I get:
> 
> Error in eval(expr, envir, enclos) : Object "csubset" not found
> 
> But if I do instead:
> 
>   cdat <- dat[dat$Diagnosis==0,]
>   cont <- lme(fixed=cform,
>                    random = ~1|StudyName,
>                       data=cdat,na.action=na.omit)
> 
> Then everything is fine.
> 
> I'm puzzled that the object can't be found.  Maybe I'm 
> overlooking something obvious?
> 
Todd,
   What version of R/nlme? I just tried the following:

library(nlme)
data(Orthodont)
csubset <- Orthodont$Sex == "Male"
fm1 <- lme(distance ~ age, data = Orthodont,
            random = ~ 1, subset = csubset)
fm2 <- lme(distance ~ age, data = Orthodont,
            random = ~ 1, subset = Sex == "Male")
fm3 <- lme(distance ~ age, data = Orthodont[csubset, ],
            random = ~ 1)

 > R.version.string
[1] "R version 1.9.0, 2004-05-06"
R> library(help = "nlme")

		Information on Package 'nlme'

Description:

Package: nlme
Version: 3.1-48
Date: 2004/01/14
<snip>

--sundar