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.
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
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