[Rd] RE: [R] Strange (non-deterministic) problem with strsplit

Henrik Bengtsson
Sat, 17 Jul 2004 01:59:47 -0000

[Moving this thread to R-devel instead]

I suspect your "random" results are due to a bug in gsub(). On my R
v1.9.0
(Rterm and Rgui) R crashes when I do

% R --vanilla
> gsub(" ", "", "abb + c | a*b", perl=TRUE)

Trying

> gsub(" ", "", "b c + d | a * b", perl=TRUE)

and I'll get NULL. With

> gsub("\\s", "", "bc + d | a * b", perl=TRUE)

it works as expected. So there is something buggy for sure.

This might have been fixed in R v1.9.1 or its patched version. (I'm still
busy to recover from a HDD crash, but, yes, I will update to Rv1.9.1. BTW,
what's the name of the error logger for Windows that is once in a while
recommended on this list and that gives more detailed errors than the
default Windows one?)

Cheers

Henrik

> -----Original Message-----
> From: r-help-bounces@stat.math.ethz.ch
> [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of hadley wickham
> Sent: Friday, July 16, 2004 10:50 PM
> To: r-help@stat.math.ethz.ch
> Subject: [R] Strange (non-deterministic) problem with strsplit
>
>
> I'm having an odd problem with strsplit (well I think it's
> strplit that's causing the problem).  When I run the code
> below as follows:  str(parseFormulaMin(y +x +d ~ b +d +e| a * b))
>
> I expect to get
> List of 3
>  $ y: chr "y+x+d"
>  $ x: chr "b+d+e"
>  $ g: chr "a*b"
>
> But about half the time I get
>
> List of 3
>  $ y: chr "y+x+d"
>  $ x: chr "b+d+e"
>  $ g: chr "a*[square box]"
> (square box not reproduced here because copy and pasting it
> seems to break my web mail)
>
> Can anyone reproduce the problem and/or suggest any solutions?
>
> parseFormula <- function(formula) {
> 	splitvars <- function(x) {
> 		strsplit(x, "\\+|\\*")[[1]]
> 	}
> 	stripwhitespace <- function(x) {
> 		gsub("\\s", "", x, perl=T)
> 	}
>
> 	vars <- stripwhitespace(as.character(formula)[3])
> 	varsplit <- strsplit(vars, "|", fixed=TRUE)[[1]]
>
> 	parts <- list(
> 		y = stripwhitespace(as.character(formula)[2]),
> 		x = varsplit[1],
> 		g = varsplit[2]
> 	)
> 	lapply(parts, splitvars)
> }
>
> Thanks,
>
> Hadley
>
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