Petr, thanks for pointing that out. Jim, you are exactly right! Thank you for catching that. I did not realize in the other replies that they were using log and not ln.
David, thank you for the lessons. I will improve my question asking skills. Thanks to all, Xu On Tue, Nov 29, 2011 at 9:31 AM, David Winsemius <dwinsem...@comcast.net>wrote: > > On Nov 29, 2011, at 2:30 AM, Xu Wang wrote: > > David, >> >> Did my reply get orphaned >> > > All replies are "orphaned". You are asked to include context if your > question relies on code that has previously been posted. > > > 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" >> > > > > >> Perhaps it's because I don't understand eval well (any good references for >> reading up on eval, parse, substitute, etc.?). >> > > It appears you need to review the help page for the `log` function. > > > But I expected it to produce >> the same as the following line: >> eval(parse(text="ln(a+b)")) >> > > It did. > > > eval(parse(text="ln(a+b)")) > > Error in eval(expr, envir, enclos) : could not find function "ln" > > >> 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)) >>>> >>>> > They both "worked" as expected. An error was appropriately reported. > > > ln(a+b) > Error: could not find function "ln" > > > log(a+b) > [1] 1.098612 > > > > > >>> Can you think of anything else we might need to know in order to >>> answer that question? >>> >> > > Some Nabble users seem to expect that the rest of Rhelp sees what they > see. They are delusional when they do so. > > -- > David. > > -- >> View this message in context: http://r.789695.n4.nabble.com/** >> Transforming-a-string-into-a-**command-tp4112183p4118294.html<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. >> >> ______________________________**________________ >> > > David Winsemius, MD > West Hartford, CT > > [[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.
