Dear list,
I am trying to create a function from a string, and have so far solved
it with eval(parse()). This works well also when using the newly created
function as an argument to another function. The trouble starts when I
want to use it with parLapply. Below is a much simplified example:
##############
fstring = "x+2"
FUN = function(x) eval(parse(text = fstring))
FUN(3)
FUN2 = function(y, func) y + func(y)
FUN2(3,FUN)
# I can also pass FUN as an argument to FUN2 when using foreach and
parallel:
library(parallel)
library(foreach)
cl = makeCluster(2, outfile = "")
ylist = list(1:3,4:6)
result = foreach(i = 1:2) %dopar% {
FUN2(ylist[[i]], FUN)
}
# But now when I wanted to change to parLapply (actually parLapplyLB)
fstring is not found anymore:
parLapply(cl, as.list(1:4), FUN2, func = FUN)
##############
I assume there is a problem with environments, the question is how to
solve this. The cleanest would be to substitute fstring with its content
in FUN, but I did not figure out how. Substitute or bquote do not seem
to do the trick, although I might not have tried them in the right way.
Any suggestions how to solve this, either how to substitute correctly,
or to completely avoid the eval(parse())?
Thanks,
Jon
--
Jon Olav Sk?ien
Joint Research Centre - European Commission
Institute for Environment and Sustainability (IES)
Land Resource Management Unit
Via Fermi 2749, TP 440, I-21027 Ispra (VA), ITALY
jon.skoien at jrc.ec.europa.eu
Disclaimer: Views expressed in this email are those of the individual and do not
necessarily represent official views of the European Commission.
Is this what you are looking for?> FUN = eval(bquote(function(x) .(parse(text = fstring)[[1]]))) > FUNfunction (x) x + 2> FUN(3)[1] 5 On Apr 16, 2013, at 09:50 , Jon Olav Skoien wrote:> Dear list, > > I am trying to create a function from a string, and have so far solved it with eval(parse()). This works well also when using the newly created function as an argument to another function. The trouble starts when I want to use it with parLapply. Below is a much simplified example: > > ############## > fstring = "x+2" > FUN = function(x) eval(parse(text = fstring)) > FUN(3) > > FUN2 = function(y, func) y + func(y) > FUN2(3,FUN) > > # I can also pass FUN as an argument to FUN2 when using foreach and parallel: > > library(parallel) > library(foreach) > cl = makeCluster(2, outfile = "") > > ylist = list(1:3,4:6) > result = foreach(i = 1:2) %dopar% { > FUN2(ylist[[i]], FUN) > } > > # But now when I wanted to change to parLapply (actually parLapplyLB) fstring is not found anymore: > parLapply(cl, as.list(1:4), FUN2, func = FUN) > ############## > > I assume there is a problem with environments, the question is how to solve this. The cleanest would be to substitute fstring with its content in FUN, but I did not figure out how. Substitute or bquote do not seem to do the trick, although I might not have tried them in the right way. Any suggestions how to solve this, either how to substitute correctly, or to completely avoid the eval(parse())? > > Thanks, > Jon > > > > -- > Jon Olav Sk?ien > Joint Research Centre - European Commission > Institute for Environment and Sustainability (IES) > Land Resource Management Unit > > Via Fermi 2749, TP 440, I-21027 Ispra (VA), ITALY > > jon.skoien at jrc.ec.europa.eu > > Disclaimer: Views expressed in this email are those of the individual and do not necessarily represent official views of the European Commission. > > ______________________________________________ > R-help at 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.-- Peter Dalgaard, Professor Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com
Thanks a lot, that seems to do exactly what I need! Best wishes, Jon On 16-Apr-13 10:21, peter dalgaard wrote:> Is this what you are looking for? > >> FUN = eval(bquote(function(x) .(parse(text = fstring)[[1]]))) >> FUN > function (x) > x + 2 >> FUN(3) > [1] 5 > > > > On Apr 16, 2013, at 09:50 , Jon Olav Skoien wrote: > >> Dear list, >> >> I am trying to create a function from a string, and have so far solved it with eval(parse()). This works well also when using the newly created function as an argument to another function. The trouble starts when I want to use it with parLapply. Below is a much simplified example: >> >> ############## >> fstring = "x+2" >> FUN = function(x) eval(parse(text = fstring)) >> FUN(3) >> >> FUN2 = function(y, func) y + func(y) >> FUN2(3,FUN) >> >> # I can also pass FUN as an argument to FUN2 when using foreach and parallel: >> >> library(parallel) >> library(foreach) >> cl = makeCluster(2, outfile = "") >> >> ylist = list(1:3,4:6) >> result = foreach(i = 1:2) %dopar% { >> FUN2(ylist[[i]], FUN) >> } >> >> # But now when I wanted to change to parLapply (actually parLapplyLB) fstring is not found anymore: >> parLapply(cl, as.list(1:4), FUN2, func = FUN) >> ############## >> >> I assume there is a problem with environments, the question is how to solve this. The cleanest would be to substitute fstring with its content in FUN, but I did not figure out how. Substitute or bquote do not seem to do the trick, although I might not have tried them in the right way. Any suggestions how to solve this, either how to substitute correctly, or to completely avoid the eval(parse())? >> >> Thanks, >> Jon >> >> >> >> -- >> Jon Olav Sk?ien >> Joint Research Centre - European Commission >> Institute for Environment and Sustainability (IES) >> Land Resource Management Unit >> >> Via Fermi 2749, TP 440, I-21027 Ispra (VA), ITALY >> >> jon.skoien at jrc.ec.europa.eu >> >> Disclaimer: Views expressed in this email are those of the individual and do not necessarily represent official views of the European Commission. >> >> ______________________________________________ >> R-help at 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.-- Jon Olav Sk?ien Joint Research Centre - European Commission Institute for Environment and Sustainability (IES) Land Resource Management Unit Via Fermi 2749, TP 440, I-21027 Ispra (VA), ITALY jon.skoien at jrc.ec.europa.eu Disclaimer: Views expressed in this email are those of the individual and do not necessarily represent official views of the European Commission.