[R] Cut intervals (character) to numeric midpoint; regex problem

[Henrique Dallazuanna]

Perhaps this shoul work too:

sapply(strsplit(gsub("^\\W|\\W$", "", testvec), ","),
function(x)sum(as.numeric(x))/2)

On Tue, Dec 1, 2009 at 5:41 PM, David Winsemius <dwinsemius at comcast.net> wrote:
> Starting with the head of a 499 element matrix whose column names are now
> the labels trom a cut() operation, I needed to get to a vector of midpoints
> to serve as the basis for plotting a calibration curve ( exp(linear
> predictor) vs.  :
>
>> dput(head(dimnames(mtcal)[2][[1]])) # was starting point
>
>
> testvec <- c("(-8.616,-3.084]", "(-3.084,-2.876]", "(-2.876,-2.756]",
> "(-2.756,-2.668]",
> "(-2.668,-2.597]", "(-2.597,-2.539]")
>
> I started this message with the thought of requesting an answer but kept
> asking myself if I really had check the docs and tested my understanding. I
> eventually solved it using the gsubfn from the gsubfn package:
>
> testintvl <-as.numeric(gsubfn("\\((-?[[:digit:]]+.?[[:digit:]]*),
> (-?[[:digit:]]+.?[[:digit:]]*)\\]",
> ~ (as.numeric(x)+as.numeric(y))/2,  testvec))
>
> # I did discover that carriage returns in the middle of the pattern will not
> give desired results, so if this is broken by your mail-client, be sure to
> rejoin in the console.
>
> The extra "?"'s after the decimal point are in there because I had 4 NA's
> around the median linear predictor:
>
>> dimnames(mtcal)[2][[1]][which(is.na(testintvl))]
> [1] "(-1.008,-1]"  "(-1,-0.9922]" "(0.9914,1]"   "(1,1.009]"
>
> So a better test vector would be:
>
> testvec <- c("(-8.616,-3.084]", "(-3.084,-2.876]", "(-2.876,-2.756]",
> "(-2.756,-2.668]",
> "(-2.668,-2.597]", "(-2.597,-2.539]", "(-1.008,-1]",  "(-1,-0.9922]",
> "(0.9914,1]", "(1,1.009]" )
>
>> testintvl
>> <-as.numeric(gsubfn("\\((-?[[:digit:]]+.?[[:digit:]]*),(-?[[:digit:]]+.?[[:digit:]]*)\\]",
> + ~ (as.numeric(x)+as.numeric(y))/2,  testvec))
>
>> testintvl
>  [1] -5.8500 -2.9800 -2.8160 -2.7120 -2.6325 -2.5680 -1.0040 -0.9961  0.9957
>  1.0045
>
> I offer this to those who may feel regex challenged (as I often do). The
> gsubfn function is pretty slick. I don't see an author listed for the
> function, but the author of the package documents is Gabor Grothendieck.
>
> --
>
> David Winsemius, MD
> Heritage Laboratories
> West Hartford, CT
>
> ______________________________________________
> 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.
>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O