On 9/14/2009 3:25 PM, Prof. John C Nash wrote:
If I run
cvec<-c("test.f", "test.sf", "try.g","try.res", "try.f")
print(cvec)
indx<-grep('\.f',cvec,perl=TRUE)
fset<-cvec[indx]
print(fset)
I get
> cvec<-c("test.f", "test.sf", "try.g","try.res", "try.f")
> print(cvec)
[1] "test.f" "test.sf" "try.g" "try.res" "try.f"
> indx<-grep("\.f",cvec,perl=TRUE)
Warning messages:
1: '\.' is an unrecognized escape in a character string
2: unrecognized escape removed from "\.f"
> fset<-cvec[indx]
> print(fset)
[1] "test.f" "test.sf" "try.f"
>
This ignores the . for which I want to test.
You need to put a \ in the string, and that takes two backslashes.
You've just been caught by the need to escape the escape to get it there:
> cvec<-c("test.f", "test.sf", "try.g","try.res", "try.f")
> indx<-grep("\\.f",cvec,perl=TRUE)
> indx
[1] 1 5
There have been proposals to have a way to enter strings in R that
doesn't require \ to be escaped, but so far no agreement on what it
should look like.
Duncan Murdoch
In perl, the function
#!/usr/bin/perl
use strict;
my @cvec=("test.f", "test.sf", "try.g","try.res", "try.f");
foreach my $elem (@cvec) {
print "$elem : ";
if ( $elem =~ '\.f' ) {
print "matches \n";
} else {
print "does not match \n";
}
}
gives
$ perl perlmatch.pl
test.f : matches
test.sf : does not match
try.g : does not match
try.res : does not match
try.f : matches
$
which does what I want. It looks like a bug (or at least a nasty
documentation failure) of "perl=TRUE".
Anyone have suggestions of how to get appropriate filtering? I need this
to automate optimization tests on large sets of test problems.
Cheers, JN
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