If there are any matches then strcapture can see if the pattern has the same number of capture expressions as the prototype has columns and give an error if not. That seems appropriate. If there are no matches, then there is no easy way to see if the prototype is compatible with the pattern, so should strcapture just assume the best and fill in the prototype with NA's? Should there be warnings? This is kind of like strptime(), which silently gives NA's when the format does not match the text input. Bill Dunlap TIBCO Software wdunlap tibco.com On Wed, Sep 21, 2016 at 2:10 PM, Michael Lawrence <lawrence.michael at gene.com> wrote:> Hi Bill, > > Thanks, another good suggestion. strcapture() now returns NAs for > non-matches. It's nice to have someone kicking the tires on that > function. > > Michael > > On Wed, Sep 21, 2016 at 12:11 PM, William Dunlap via R-devel > <r-devel at r-project.org> wrote: > > Michael, thanks for looking at my first issue with utils::strcapture. > > > > Another issue is how it deals with lines that don't match the pattern. > > Currently it gives an error > > > >> strcapture("(.+) (.+)", c("One 1", "noSpaceInLine", "Three 3"), > > proto=list(Name="", Number=0)) > > Error in strcapture("(.+) (.+)", c("One 1", "noSpaceInLine", "Three > 3"), : > > number of matches does not always match ncol(proto) > > > > First, isn't the 'number of matches' the number of parenthesized > > subpatterns in the regular expression? I thought that if the entire > > pattern matches then the subpatterns without matches would be > > shown as matches at position 0 with length 0. Hence either the > > pattern is compatible with the prototype or it isn't, it does not depend > > on the text input. E.g., > > > >> regexec("^(([[:alpha:]]+)|([[:digit:]]+))$", c("Twelve", "12", "Z280")) > > [[1]] > > [1] 1 1 1 0 > > attr(,"match.length") > > [1] 6 6 6 0 > > attr(,"useBytes") > > [1] TRUE > > > > [[2]] > > [1] 1 1 0 1 > > attr(,"match.length") > > [1] 2 2 0 2 > > attr(,"useBytes") > > [1] TRUE > > > > [[3]] > > [1] -1 > > attr(,"match.length") > > [1] -1 > > attr(,"useBytes") > > [1] TRUE > > > > Second, an error message like 'some lines were bad' is not very helpful. > > Should it put NA's in all the columns of the current output row if the > > input line didn't match the pattern and perhaps warn the user that there > > were problems? The user could then look for rows of NA's to see where > the > > problems were. > > > > Bill Dunlap > > TIBCO Software > > wdunlap tibco.com > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-devel at r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel >[[alternative HTML version deleted]]
The new behavior is that it yields NAs when the pattern does not match (like strptime) and for empty captures in a matching pattern it yields the empty string, which is consistent with regmatches(). Michael On Wed, Sep 21, 2016 at 2:21 PM, William Dunlap <wdunlap at tibco.com> wrote:> If there are any matches then strcapture can see if the pattern has the same > number of capture expressions as the prototype has columns and give an > error if not. That seems appropriate. > > If there are no matches, then there is no easy way to see if the prototype > is compatible with the pattern, so should strcapture just assume the best > and fill in the prototype with NA's? > > Should there be warnings? This is kind of like strptime(), which silently > gives NA's when the format does not match the text input. > > > Bill Dunlap > TIBCO Software > wdunlap tibco.com > > On Wed, Sep 21, 2016 at 2:10 PM, Michael Lawrence > <lawrence.michael at gene.com> wrote: >> >> Hi Bill, >> >> Thanks, another good suggestion. strcapture() now returns NAs for >> non-matches. It's nice to have someone kicking the tires on that >> function. >> >> Michael >> >> On Wed, Sep 21, 2016 at 12:11 PM, William Dunlap via R-devel >> <r-devel at r-project.org> wrote: >> > Michael, thanks for looking at my first issue with utils::strcapture. >> > >> > Another issue is how it deals with lines that don't match the pattern. >> > Currently it gives an error >> > >> >> strcapture("(.+) (.+)", c("One 1", "noSpaceInLine", "Three 3"), >> > proto=list(Name="", Number=0)) >> > Error in strcapture("(.+) (.+)", c("One 1", "noSpaceInLine", "Three 3"), >> > : >> > number of matches does not always match ncol(proto) >> > >> > First, isn't the 'number of matches' the number of parenthesized >> > subpatterns in the regular expression? I thought that if the entire >> > pattern matches then the subpatterns without matches would be >> > shown as matches at position 0 with length 0. Hence either the >> > pattern is compatible with the prototype or it isn't, it does not depend >> > on the text input. E.g., >> > >> >> regexec("^(([[:alpha:]]+)|([[:digit:]]+))$", c("Twelve", "12", "Z280")) >> > [[1]] >> > [1] 1 1 1 0 >> > attr(,"match.length") >> > [1] 6 6 6 0 >> > attr(,"useBytes") >> > [1] TRUE >> > >> > [[2]] >> > [1] 1 1 0 1 >> > attr(,"match.length") >> > [1] 2 2 0 2 >> > attr(,"useBytes") >> > [1] TRUE >> > >> > [[3]] >> > [1] -1 >> > attr(,"match.length") >> > [1] -1 >> > attr(,"useBytes") >> > [1] TRUE >> > >> > Second, an error message like 'some lines were bad' is not very helpful. >> > Should it put NA's in all the columns of the current output row if the >> > input line didn't match the pattern and perhaps warn the user that there >> > were problems? The user could then look for rows of NA's to see where >> > the >> > problems were. >> > >> > Bill Dunlap >> > TIBCO Software >> > wdunlap tibco.com >> > >> > [[alternative HTML version deleted]] >> > >> > ______________________________________________ >> > R-devel at r-project.org mailing list >> > https://stat.ethz.ch/mailman/listinfo/r-devel > >
I noticed a problem in the strcapture from R-devel (2016-09-27 r71386),
when the text contains a missing value and perl=TRUE.
{
# NA in text input should map to row of NA's in output, without
warning
r9p <- strcapture(perl = TRUE, "(.).* ([[:digit:]]+)",
c("One 1", NA,
"Fifty 50"), data.frame(Initial=factor(), Number=numeric()))
e9p <- structure(list(Initial = structure(c(2L, NA, 1L), .Label
c("F", "O"), class = "factor"),
Number = c(1, NA, 50)),
row.names = c(NA, -3L),
class = "data.frame")
all.equal(e9p, r9p)
}
#Error in if (any(ind)) { : missing value where TRUE/FALSE needed
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Wed, Sep 21, 2016 at 2:32 PM, Michael Lawrence <lawrence.michael at
gene.com> wrote:
> The new behavior is that it yields NAs when the pattern does not match
> (like strptime) and for empty captures in a matching pattern it yields
> the empty string, which is consistent with regmatches().
>
> Michael
>
> On Wed, Sep 21, 2016 at 2:21 PM, William Dunlap <wdunlap at
tibco.com> wrote:
> > If there are any matches then strcapture can see if the pattern has
the
> same
> > number of capture expressions as the prototype has columns and give an
> > error if not. That seems appropriate.
> >
> > If there are no matches, then there is no easy way to see if the
> prototype
> > is compatible with the pattern, so should strcapture just assume the
best
> > and fill in the prototype with NA's?
> >
> > Should there be warnings? This is kind of like strptime(), which
> silently
> > gives NA's when the format does not match the text input.
> >
> >
> > Bill Dunlap
> > TIBCO Software
> > wdunlap tibco.com
> >
> > On Wed, Sep 21, 2016 at 2:10 PM, Michael Lawrence
> > <lawrence.michael at gene.com> wrote:
> >>
> >> Hi Bill,
> >>
> >> Thanks, another good suggestion. strcapture() now returns NAs for
> >> non-matches. It's nice to have someone kicking the tires on
that
> >> function.
> >>
> >> Michael
> >>
> >> On Wed, Sep 21, 2016 at 12:11 PM, William Dunlap via R-devel
> >> <r-devel at r-project.org> wrote:
> >> > Michael, thanks for looking at my first issue with
utils::strcapture.
> >> >
> >> > Another issue is how it deals with lines that don't match
the pattern.
> >> > Currently it gives an error
> >> >
> >> >> strcapture("(.+) (.+)", c("One 1",
"noSpaceInLine", "Three 3"),
> >> > proto=list(Name="", Number=0))
> >> > Error in strcapture("(.+) (.+)", c("One
1", "noSpaceInLine", "Three
> 3"),
> >> > :
> >> > number of matches does not always match ncol(proto)
> >> >
> >> > First, isn't the 'number of matches' the number
of parenthesized
> >> > subpatterns in the regular expression? I thought that if the
entire
> >> > pattern matches then the subpatterns without matches would be
> >> > shown as matches at position 0 with length 0. Hence either
the
> >> > pattern is compatible with the prototype or it isn't, it
does not
> depend
> >> > on the text input. E.g.,
> >> >
> >> >> regexec("^(([[:alpha:]]+)|([[:digit:]]+))$",
c("Twelve", "12",
> "Z280"))
> >> > [[1]]
> >> > [1] 1 1 1 0
> >> > attr(,"match.length")
> >> > [1] 6 6 6 0
> >> > attr(,"useBytes")
> >> > [1] TRUE
> >> >
> >> > [[2]]
> >> > [1] 1 1 0 1
> >> > attr(,"match.length")
> >> > [1] 2 2 0 2
> >> > attr(,"useBytes")
> >> > [1] TRUE
> >> >
> >> > [[3]]
> >> > [1] -1
> >> > attr(,"match.length")
> >> > [1] -1
> >> > attr(,"useBytes")
> >> > [1] TRUE
> >> >
> >> > Second, an error message like 'some lines were bad'
is not very
> helpful.
> >> > Should it put NA's in all the columns of the current
output row if the
> >> > input line didn't match the pattern and perhaps warn the
user that
> there
> >> > were problems? The user could then look for rows of NA's
to see where
> >> > the
> >> > problems were.
> >> >
> >> > Bill Dunlap
> >> > TIBCO Software
> >> > wdunlap tibco.com
> >> >
> >> > [[alternative HTML version deleted]]
> >> >
> >> > ______________________________________________
> >> > R-devel at r-project.org mailing list
> >> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
> >
>
[[alternative HTML version deleted]]