Petr Pikal wrote: > Hi > > yes you are correct, I remembered there is something with eval from > older posts but did not find a connection to parse from eval help > page. Shouldn't there be a link? Or even an example?
would be a good thing to do (there only is a link from parse to eval). after all eval(parse(text = some_string)) is what many users (which might come from matlab/octave where this _would_ suffice) want when they try out eval(some_string)). and a standard eval(parse(text=...) example on the eval manpage (where most people probably would look, would be very good. > > Best regards > Petr > > > On 15 Jun 2006 at 17:21, Dimitris Rizopoulos wrote: > > From: "Dimitris Rizopoulos" <[EMAIL PROTECTED]> > To: "Petr Pikal" <[EMAIL PROTECTED]>, <[EMAIL PROTECTED]> > Copies to: <r-help@stat.math.ethz.ch> > Subject: Re: [R] Access and assign list sub-elements using a > string suchas "l$a$b" > Date sent: Thu, 15 Jun 2006 17:21:26 +0200 > >> ----- Original Message ----- >> From: "Petr Pikal" <[EMAIL PROTECTED]> >> To: "Gregory Jefferis" <[EMAIL PROTECTED]> >> Cc: <r-help@stat.math.ethz.ch> >> Sent: Thursday, June 15, 2006 4:56 PM >> Subject: Re: [R] Access and assign list sub-elements using a string >> suchas "l$a$b" >> >> >>> Hi >>> very, very close >>> >>> >>> On 15 Jun 2006 at 13:27, Gregory Jefferis wrote: >>> >>> Date sent: Thu, 15 Jun 2006 13:27:05 +0100 >>> From: Gregory Jefferis <[EMAIL PROTECTED]> >>> To: "[EMAIL PROTECTED]" >>> <[EMAIL PROTECTED]> >>> Forwarded to: <r-help@stat.math.ethz.ch> >>> Forwarded by: Gregory Jefferis <[EMAIL PROTECTED]> >>> Date forwarded: Thu, 15 Jun 2006 14:54:13 +0100 >>> Subject: [R] Access and assign list sub-elements using a >>> string such as "l$a$b" >>> >>>> If I have a list I can set a sub-element as follows on the command >>>> line: >>>> >>>> people=list() >>>> people$tom$hair="brown" >>>> people >>>> >>>> But what if I have a string containing the name of the sub-element >>>> that I want to access? >>>> >>>> subel= "people$tom$hair" >>>> >>>> get(subel) # returns error >>>> assign(subel,"red") # silent but doesn't change list >>>> people >>> See what happens when >>> >>> people<-assign(subel, "red") >> but I think this is not what Greg wanted; the above just assigns "red" >> to object 'people' (i.e., check `str(assign(subel, "red"))'). If I >> understood correctly, the following could be of help: >> >> people <- list() >> people$tom$hair <- "brown" >> people >> ################# >> subel <- "people$tom$hair" >> eval(parse(text = subel)) >> eval(parse(text = paste(subel, "<- 'red'"))) >> people >> >> >> Best, >> Dimitris >> >> >> ---- >> Dimitris Rizopoulos >> Ph.D. Student >> Biostatistical Centre >> School of Public Health >> Catholic University of Leuven >> >> Address: Kapucijnenvoer 35, Leuven, Belgium >> Tel: +32/(0)16/336899 >> Fax: +32/(0)16/337015 >> Web: http://med.kuleuven.be/biostat/ >> http://www.student.kuleuven.be/~m0390867/dimitris.htm >> >> >>> HTH >>> Petr >>> >>> >>>> The attempts above using assign/get won't do what I am trying to do >>>> [nor according to the help should they]. I would be very grateful >>>> for any suggestions. Many thanks, >>>> >>>> Greg. >>>> >>>> -- >>>> Gregory Jefferis, PhD and: >>>> Research Fellow >>>> Department of Zoology St John's >>>> College University of Cambridge Cambridge Downing Street >>>> CB2 1TP Cambridge, CB2 3EJ United Kingdom >>>> >>>> Lab Tel: +44 (0)1223 336683 Office: +44 (0)1223 >>>> 339899 Lab Fax: +44 (0)1223 336676 >>>> >>>> http://www.zoo.cam.ac.uk/zoostaff/jefferis.html >>>> [EMAIL PROTECTED] >>>> >>>> ______________________________________________ >>>> 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 >>> Petr Pikal >>> [EMAIL PROTECTED] >>> >>> ______________________________________________ >>> 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 >>> >> >> Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm >> > > Petr Pikal > [EMAIL PROTECTED] > > ______________________________________________ > 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 ______________________________________________ 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
