Hi Alrik,
On 02/28/2015 11:06 PM, Alrik Thiem wrote:
Dear Hervé,
Many thanks for your suggestion. Gabor Grothendieck proposed a simple
one-liner that works perfectly for my purposes:
gsub("(\\b[a-oq-z][a-z0-9]*)", "1-\\U\\1", x, perl = TRUE)
where x is the respective string.
Sounds good. I didn't realize that you also wanted to prefix the lower
case letters with "1 - " so my solution was not doing the right thing
anyway. Here is the corrected solution, just in case:
library(Biostrings)
funnyReplace <- function(x, protected_words)
{
x <- BString(x)
## Extract the substrings to modify (target substrings).
protected_regions <- reduce(do.call("c", lapply(protected_words,
matchPattern, x)))
target_regions <- ranges(gaps(protected_regions))
target_substrings <- extractAt(x, target_regions)
## Modify them (using a reg exp almost like Gabbor's except
## that "p" is not treated as an exception).
target_substrings <- gsub("(\\b[a-z][a-z0-9]*)", "1 - \\U\\1",
target_substrings, perl=TRUE)
## Replace in original string.
x <- replaceAt(x, target_regions, target_substrings)
as.character(x)
}
Then:
> x <- "pmin(pmax(pmin(x1, X2), pmin(X3, X4)) == Y, pmax(Z1, z1))"
> funnyReplace(x, c("pmin", "pmax"))
[1] "pmin(pmax(pmin(1 - X1, X2), pmin(X3, X4)) == Y, pmax(Z1, 1 - Z1))"
It works even if a variable name starts with a "p":
> funnyReplace("pmin(p)", c("pmin", "pmax"))
[1] "pmin(1 - P)"
and you can specify an arbitrary number of protected words.
Cheers,
H.
Best wishes,
Alrik
-----Ursprüngliche Nachricht-----
Von: Hervé Pagès [mailto:hpa...@fredhutch.org]
Gesendet: Samstag, 28. Februar 2015 23:29
An: Alrik Thiem; r-help@r-project.org
Betreff: Re: [R] Substring replacement in string
Hi Alrik,
With the Biostrings/IRanges infrastructure (Bioconductor packages), you
can do this with:
library(Biostrings)
x0 <- BString("pmin(pmax(pmin(x1, X2), pmin(X3, X4)) == Y, pmax(Z1,
z1))")
donttouch_words <- c("pmin", "pmax")
## Extract the substrings to modify (target substrings).
donttouch_regions <- reduce(do.call("c", lapply(donttouch_words,
matchPattern, x0)))
target_regions <- ranges(gaps(donttouch_regions))
target_substrings <- extractAt(x0, target_regions)
## Modify them.
old <- paste0(letters, collapse="")
new <- paste0(LETTERS, collapse="")
target_substrings <- chartr(old, new, target_substrings)
## Replace in original string.
x1 <- replaceAt(x0, target_regions, target_substrings)
Then:
> x1
57-letter "BString" instance
seq: pmin(pmax(pmin(X1, X2), pmin(X3, X4)) == Y, pmax(Z1, Z1))
> as.character(x1)
[1] "pmin(pmax(pmin(X1, X2), pmin(X3, X4)) == Y, pmax(Z1, Z1))"
Hope this helps,
H.
On 02/27/2015 02:19 PM, Alrik Thiem wrote:
Dear R-help list,
I would like to replace all lower-case letters in a string that are not
part
of certain fixed expressions. For example, I have the string:
"pmin(pmax(pmin(x1, X2), pmin(X3, X4)) == Y, pmax(Z1, z1))"
Where I would like to replace all lower-case letters that do not belong to
the functions "pmin" and "pmax" by 1 - toupper(...) to get
"pmin(pmax(pmin(1 - X1, X2), pmin(X3, X4)) == Y, pmax(Z1, 1 - Z1))"
Any ideas on how I could achieve that?
Many thanks and best wishes,
Alrik
********************************
Alrik Thiem
Post-Doctoral Researcher
Department of Philosophy
University of Geneva
Rue de Candolle 2
CH-1211 Geneva
+41 76 527 80 83
http://www.alrik-thiem.net
http://www.compasss.org
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--
Hervé Pagès
Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024
E-mail: hpa...@fredhutch.org
Phone: (206) 667-5791
Fax: (206) 667-1319
______________________________________________
R-help@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.
