Hi > > Did my reply get orphaned or are you trying to help me realize that asking > why something does not work is not a straightforward question? I'll try to > cover both bases. > > I'll focus just on the first case that I don't understand. Suppose we have > s<- "ln(a+b)" > a<-1 > b<-2 > eval(parse(text=s)) > Error in eval(expr, envir, enclos) : could not find function "ln"
What is function ln supposed to do and to what package it belongs. I get > ?ln No documentation for ‘ln’ in specified packages and libraries: you could try ‘??ln’ but it does not mean that ln is not used elsewhere. Regards Petr > > Perhaps it's because I don't understand eval well (any good references for > reading up on eval, parse, substitute, etc.?). But I expected it to produce > the same as the following line: > eval(parse(text="ln(a+b)")) > > Xu > > > David Winsemius wrote > > > > On Nov 29, 2011, at 2:00 AM, Xu Wang wrote: > > > >> Why don't the following two commands work? > >> > >> eval(parse(text=s)) > >> eval(as.expression(s)) > >> > > > > Can you think of anything else we might need to know in order to > > answer that question? > > > > -- > > > > David Winsemius, MD > > West Hartford, CT > > > > ______________________________________________ > > R-help@ 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. > > > > > -- > View this message in context: http://r.789695.n4.nabble.com/Transforming- > a-string-into-a-command-tp4112183p4118294.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.
