Gabor, That's very nice! I like your my.transform much better. Too bad about the incompatibility. Swapping that out would no doubt break some existing programs. I love that old joke, "God was able to create the universe in just 6 days only because he didn't have an installed base to worry about!"
Cheers, Bob > -----Original Message----- > From: Gabor Grothendieck [mailto:[EMAIL PROTECTED] > Sent: Sunday, September 02, 2007 10:47 AM > To: Muenchen, Robert A (Bob) > Cc: r-help@stat.math.ethz.ch > Subject: Re: [R] Comparing "transform" to "with" > > Try this version of transform. In the first test we show > it works on your example but we have used the head of the built in > anscombe data set. The second and third show that > it necessarily is incompatible with transform because transform > always looks up variables in DF first whereas my.transform looks > up the computed ones first. > > my.transform <- function(DF, ...) { > f <- function(){} > formals(f) <- eval(substitute(as.pairlist(c(alist(...), DF)))) > body(f) <- substitute(modifyList(DF, data.frame(...))) > f() > } > > # test > a <- head(anscombe) > # 1 > my.transform(a, sum1 = x1+x2+x3+x4, sum2 = y1+y2+y3+y4, total = > sum1+sum2) > # 2 > my.transform(a, y2 = y1, y3 = y2) > # 3 > transform(a, y2 = y1, y3 = y2) # different > > > On 9/1/07, Muenchen, Robert A (Bob) <[EMAIL PROTECTED]> wrote: > > Hi All, > > > > I've been successfully using the with function for analyses and the > > transform function for multiple transformations. Then I thought, why > not > > use "with" for both? I ran into problems & couldn't figure them out > from > > help files or books. So I created a simplified version of what I'm > > doing: > > > > rm( list=ls() ) > > x1<-c(1,3,3) > > x2<-c(3,2,1) > > x3<-c(2,5,2) > > x4<-c(5,6,9) > > myDF<-data.frame(x1,x2,x3,x4) > > rm(x1,x2,x3,x4) > > ls() > > myDF > > > > This creates two new variables just fine" > > > > transform(myDF, > > sum1=x1+x2, > > sum2=x3+x4 > > ) > > > > This next code does not see sum1, so it appears that "transform" > cannot > > see the variables that it creates. Would I need to transform new > > variables in a second pass? > > > > transform(myDF, > > sum1=x1+x2, > > sum2=x3+x4, > > total=sum1+sum2 > > ) > > > > Next I'm trying the same thing using "with". It doesn't not work but > > also does not generate error messages, giving me the impression that > I'm > > doing something truly idiotic: > > > > with(myDF, { > > sum1<-x1+x2 > > sum2<-x3+x4 > > total <- sum1+sum2 > > } ) > > myDF > > ls() > > > > Then I thought, perhaps one of the advantages of "transform" is that > it > > works on the left side of the equation without using a longer name > like > > myDF$sum1. "with" probably doesn't do that, so I use the longer form > > below. It also does not work and generates no error messages. > > > > # Try it again, writing vars to myDF explicitly. > > # It generates no errors, and no results. > > with(myDF, { > > myDF$sum1<-x1+x2 > > myDF$sum2<-x3+x4 > > myDF$total <- myDF$sum1+myDF$sum2 > > } ) > > myDF > > ls() > > > > I would appreciate some advice about the relative roles of these two > > functions & why my attempts with "with" have failed. > > > > Thanks! > > Bob > > > > ========================================================= > > Bob Muenchen (pronounced Min'-chen), Manager > > Statistical Consulting Center > > U of TN Office of Information Technology > > 200 Stokely Management Center, Knoxville, TN 37996-0520 > > Voice: (865) 974-5230 > > FAX: (865) 974-4810 > > Email: [EMAIL PROTECTED] > > Web: http://oit.utk.edu/scc, > > News: http://listserv.utk.edu/archives/statnews.html > > > > ______________________________________________ > > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.
