[R] string pattern matching

Thu Mar 23 16:56:11 CET 2017

Oh, I see the utility of that now. Definitely will be using "term.labels"
(which I was not aware of). Thanks!

On Thu, Mar 23, 2017 at 9:48 AM, William Dunlap <wdunlap at tibco.com> wrote:

> If you are trying to see if one model nested in another then I think
> looking at the 'term.labels' attribute of terms(formula) is the way to
> go.  Most formula-based modelling functions store the output of
> terms(formula) in their output and many supply a method for the terms
> function that extracts that from their output.
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
>
>
> On Thu, Mar 23, 2017 at 6:37 AM, Joe Ceradini <joeceradini at gmail.com>
> wrote:
> > Thanks for the additional response, Bill. I did not want to bog down
> > the question with the full context of the function. Briefly, given a
> > set of nested and non-nested regression models, I want to compare AIC
> > (bigger model - smaller model) and do an LRT for all the nested models
> > that differ by a single predictor. All models, nested or not, would
> > also have an AIC value (I am aware of the critiques of mixing p-value
> > hypothesis testing and information criteria). So, not quite
> > MuMIn::dredge. The tricky part, for me, has been doing the comparisons
> > for only the nested models in a set that contains nested and
> > non-nested. I made some progress with the function, so I'll refrain
> > from bugging the list with the whole thing unless (when) I'm stuck
> > again.
> >
> > For those interested in the motivation, I'm running with the idea of
> > trying to flag uninformative parameters which "steal" AIC model
> > weight, and potentially result in a misleading model set, depending
> > how the reader interprets the set.
> > Arnold, T. W. 2010. Uninformative parameters and model selection using
> > Akaike’s information criterion. Journal of Wildlife Management
> > 74:1175–1178.
> > Murtaugh, P. 2014. In defense of P values. Ecology 95:611–617.
> >
> > Joe
> >
> > On Wed, Mar 22, 2017 at 9:11 AM, William Dunlap <wdunlap at tibco.com>
> wrote:
> >> You did not describe the goal of your pattern matching.  Were you trying
> >> to match any string that could be interpreted as an R expression
> containing
> >> X1 and X3 as additive terms?   If so, you could turn the string into a
> one-sided
> >> formula and use the terms() function.  E.g.,
> >>
> >> f <- function(string) {
> >>     fmla <- as.formula(paste("~", string))
> >>     term.labels <- attr(terms(fmla), "term.labels")
> >>     all(c("X1","X3") %in% term.labels)
> >> }
> >>
> >>> f("X3 + X2 + X1")
> >> [1] TRUE
> >>> f("- X3 + X2 + X1")
> >> [1] FALSE
> >>> f("X3 + X2 + log(X1)")
> >> [1] FALSE
> >>> f("X3 + X2 + log(X1) + X1")
> >> [1] TRUE
> >> Bill Dunlap
> >> TIBCO Software
> >> wdunlap tibco.com
> >>
> >>
> >> On Wed, Mar 22, 2017 at 6:39 AM, Joe Ceradini <joeceradini at gmail.com>
> wrote:
> >>> Wow. Thanks to everyone (Jim, Ng Bo Lin, Bert, David, and Ulrik) for
> >>> all the quick and helpful responses. They have given me a better
> >>> understanding of regular expressions, and certainly answered my
> >>> question.
> >>>
> >>> Joe
> >>>
> >>> On Wed, Mar 22, 2017 at 12:22 AM, Ulrik Stervbo <
> ulrik.stervbo at gmail.com> wrote:
> >>>> Hi Joe,
> >>>>
> >>>> you could also rethink your pattern:
> >>>>
> >>>> grep("x1 \\+ x2", test, value = TRUE)
> >>>>
> >>>> grep("x1 \\+ x", test, value = TRUE)
> >>>>
> >>>> grep("x1 \\+ x[0-9]", test, value = TRUE)
> >>>>
> >>>> HTH
> >>>> Ulrik
> >>>>
> >>>> On Wed, 22 Mar 2017 at 02:10 Jim Lemon <drjimlemon at gmail.com> wrote:
> >>>>>
> >>>>> Hi Joe,
> >>>>> This may help you:
> >>>>>
> >>>>> test <- c("x1", "x2", "x3", "x1 + x2 + x3")
> >>>>> multigrep<-function(x1,x2) {
> >>>>>  xbits<-unlist(strsplit(x1," "))
> >>>>>  nbits<-length(xbits)
> >>>>>  xans<-rep(FALSE,nbits)
> >>>>>  for(i in 1:nbits) if(length(grep(xbits[i],x2))) xans[i]<-TRUE
> >>>>>  return(all(xans))
> >>>>> }
> >>>>> multigrep("x1 + x3","x1 + x2 + x3")
> >>>>> [1] TRUE
> >>>>> multigrep("x1 + x4","x1 + x2 + x3")
> >>>>> [1] FALSE
> >>>>>
> >>>>> Jim
> >>>>>
> >>>>> On Wed, Mar 22, 2017 at 10:50 AM, Joe Ceradini <
> joeceradini at gmail.com>
> >>>>> wrote:
> >>>>> > Hi Folks,
> >>>>> >
> >>>>> > Is there a way to find "x1 + x2 + x3" given "x1 + x3" as the
> pattern?
> >>>>> > Or is that a ridiculous question, since I'm trying to find
> something
> >>>>> > based on a pattern that doesn't exist?
> >>>>> >
> >>>>> > test <- c("x1", "x2", "x3", "x1 + x2 + x3")
> >>>>> > test
> >>>>> > [1] "x1"           "x2"           "x3"           "x1 + x2 + x3"
> >>>>> >
> >>>>> > grep("x1 + x2", test, fixed=TRUE, value = TRUE)
> >>>>> > [1] "x1 + x2 + x3"
> >>>>> >
> >>>>> >
> >>>>> > But what if only have "x1 + x3" as the pattern and still want to
> >>>>> > return "x1 + x2 + x3"?
> >>>>> >
> >>>>> > grep("x1 + x3", test, fixed=TRUE, value = TRUE)
> >>>>> > character(0)
> >>>>> >
> >>>>> > I'm sure this looks like an odd question. I'm trying to build a
> >>>>> > function and stuck on this. Rather than dropping the whole
> function on
> >>>>> > the list, I thought I'd try one piece I needed help
> with...although I
> >>>>> > suspect that this question itself probably does bode well for my
> >>>>> > function :)
> >>>>> >
> >>>>> > Thanks!
> >>>>> > Joe
> >>>>> >
> >>>>> > ______________________________________________
> >>>>> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >>>>> > 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 at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >>>>> 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.
> >>>
> >>>
> >>>
> >>> --
> >>> Cooperative Fish and Wildlife Research Unit
> >>> Zoology and Physiology Dept.
> >>> University of Wyoming
> >>> JoeCeradini at gmail.com / 914.707.8506
> >>> wyocoopunit.org
> >>>
> >>> ______________________________________________
> >>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >>> 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.
> >
> >
> >
> > --
> > Cooperative Fish and Wildlife Research Unit
> > Zoology and Physiology Dept.
> > University of Wyoming
> > JoeCeradini at gmail.com / 914.707.8506
> > wyocoopunit.org
>

-- 
Cooperative Fish and Wildlife Research Unit
Zoology and Physiology Dept.
University of Wyoming
JoeCeradini at gmail.com / 914.707.8506
wyocoopunit.org

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