[Rd] data.frame within a function (PR#9294) (cont'd)

[Prof Brian Ripley]

This is not to do with your subject line, and not a bug (and PR#9294 as 
been closed).  You don't even say what you think the 'issue' is: it seems 
to be your lack of understanding of the scope rules.

I get

> f2()
ok
Error in inherits(x, "data.frame") : object "dtf" not found

which is quite correct: dtf is not visible from the body of f() where you 
call update(evaluate=T) (the default, and use TRUE please).  This is why 
update has an 'evaluate' argument, so you can manage the scope used.


On Thu, 30 Nov 2006, Riyan Cheng wrote:

> This continues the message "data.frame within a function (PR#9294)" that
> was posted on 2006/10/12. Duncan Murdoch kindly replied. I'm using the
> current version R 2.4.0, but the same issue exists. Just copy and paste
> the following code under R, and compare the output of f1() and f2() and
> the output of f3() and f4(). Does anybody have any idea? Thanks.
>
> ###################################################
> # R code for demonstration only #
> ###########################
>
> rmvnorm<- function (n, mean = rep(0, nrow(sigma)), sigma =
> diag(length(mean))){
>  if (nrow(sigma) != ncol(sigma)) {
>    stop("sigma must be a square matrix")
>  }
>  if (length(mean) != nrow(sigma)) {
>    stop("mean and sigma have non-conforming size")
>  }
>  ev <- eigen(sigma, sym = TRUE)$values
>  if (!all(ev >= -sqrt(.Machine$double.eps) * abs(ev[1])))
>    warning("sigma is numerically not positive definite")
>  sigsvd <- svd(sigma)
>  retval <- t(sigsvd$v %*% (t(sigsvd$u) * sqrt(sigsvd$d)))
>  retval <- matrix(rnorm(n * ncol(sigma)), nrow = n) %*% retval
>  retval <- sweep(retval, 2, mean, "+")
>  retval
> }
>
> f<- function(obj){
>     update(obj,~ .+x,evaluate=T); cat("also ok\n")
> }
>
> #########################
> # compare f1() and f2() #
> #########################
> f1<- function(){
>     x<- rnorm(10)
>     y<- rmvnorm(10,mean=c(1,2)); colnames(y)<- paste("y",1:2,sep="")
> #c("y1","y2")
>     dtf<- data.frame(y,x)
>     lm1<- lm(cbind(y1,y2)~1,data=dtf); cat("ok\n")
>
>     update(lm1,~ .+x,evaluate=T); cat("also ok\n") # only this line is
> different
> }
> f2<- function(){
>     x<- rnorm(10)
>     y<- rmvnorm(10,mean=c(1,2)); colnames(y)<- paste("y",1:2,sep="")
> #c("y1","y2")
>     dtf<- data.frame(y,x)
>     lm1<- lm(cbind(y1,y2)~1,data=dtf); cat("ok\n")
>
>     f(lm1) # only this line is different
> }
>
> f1()
> f2()
>
> #########################
> # compare f3() and f4() #
> #########################
> f3<- function(){
>     x<- rnorm(10)
>     y<- rmvnorm(10,mean=c(1,2)); colnames(y)<- paste("y",1:2,sep="")
> #c("y1","y2")
>     lm1<- lm(cbind(y1,y2)~1,data=data.frame(y,x)); cat("ok\n")
>
>     update(lm1,~ .+x,evaluate=T); cat("also ok\n") # only this line is
> different
> }
> f4<- function(){
>     x<- rnorm(10)
>     y<- rmvnorm(10,mean=c(1,2)); colnames(y)<- paste("y",1:2,sep="")
> #c("y1","y2")
>     lm1<- lm(cbind(y1,y2)~1,data=data.frame(y,x)); cat("ok\n")
>
>     f(lm1) # only this line is different
> }
>
> f3()
> f4()
>
> #########
> # the end #
> #########
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595