Peng Yu
2009-Nov-06 16:08 UTC
[R] What is the best way to delete strings in a string list that that match certain pattern?
On Fri, Nov 6, 2009 at 3:05 AM, Diez B. Roggisch <deets at nospam.web.de> wrote:> Peng Yu schrieb: >> >> Suppose I have a list of strings, A. I want to compute the list (call >> it B) of strings that are elements of A but doesn't match a regex. I >> could use a for loop to do so. In a functional language, there is way >> to do so without using the for loop. > > Nonsense. For processing over each element, you have to loop over them, > either with or without growing a call-stack at the same time. > > FP languages can optimize away the stack-frame-growth (tail recursion) - but > this isn't reducing complexity in any way. > > So use a loop, either directly, or using a list-comprehension.What is a list-comprehension?
Charles C. Berry
2009-Nov-06 16:22 UTC
[R] What is the best way to delete strings in a string list that that match certain pattern?
On Fri, 6 Nov 2009, Peng Yu wrote:> On Fri, Nov 6, 2009 at 3:05 AM, Diez B. Roggisch <deets at nospam.web.de> wrote: >> Peng Yu schrieb: >>> >>> Suppose I have a list of strings, A. I want to compute the list (call >>> it B) of strings that are elements of A but doesn't match a regex. I >>> could use a for loop to do so. In a functional language, there is way >>> to do so without using the for loop. >> >> Nonsense. For processing over each element, you have to loop over them, >> either with or without growing a call-stack at the same time. >> >> FP languages can optimize away the stack-frame-growth (tail recursion) - but >> this isn't reducing complexity in any way. >> >> So use a loop, either directly, or using a list-comprehension. > > What is a list-comprehension?http://lmgtfy.com/?q=list+comprehension> > ______________________________________________ > 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. >Charles C. Berry (858) 534-2098 Dept of Family/Preventive Medicine E mailto:cberry at tajo.ucsd.edu UC San Diego http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego 92093-0901