Hi!
I'm trying to write a custom function that applies SubStr to a string, and
then depending on the arguments, converts the output to a number.
The substring part of my code works fine, but it's not converting the way I
want to --
options('stringsAsFactors'=FALSE)
require(data.table)
substr_typeswitch <- function(x, start, stop, typeto='chr')
{
tmpvar <- substr(x=x, start=start, stop=stop)
tmpvar <- switch(typeto, num=as.numeric(tmpvar), tmpvar)
return(tmpvar)
}
startpos <- c(01, 03)
endpos <- c(02, 04)
typelist <- c('chr', 'num')
startdata <- as.data.table(c('aa01', 'bb02'))
enddata_want <- as.data.table(mapply(substr_typeswitch, startdata,
startpos, endpos, typelist))
If I examine enddata_want --
> str(enddata_want)
Classes ?data.table? and 'data.frame': 2 obs. of 2 variables:
$ V1: chr "aa" "bb"
$ NA: chr "1" "2"
- attr(*, ".internal.selfref")=<externalptr>
"1" and "2" are being stored as character, and not as
number.
Can anyone help me understand what I'm doing wrong?
Thank you!
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On Feb 10, 2015, at 3:58 PM, Brian Trautman wrote:> Hi! > > I'm trying to write a custom function that applies SubStr to a string, and > then depending on the arguments, converts the output to a number. > > The substring part of my code works fine, but it's not converting the way I > want to -- > > options('stringsAsFactors'=FALSE) > require(data.table) > > substr_typeswitch <- function(x, start, stop, typeto='chr') > { > tmpvar <- substr(x=x, start=start, stop=stop) > tmpvar <- switch(typeto, num=as.numeric(tmpvar), tmpvar) > return(tmpvar) > } > startpos <- c(01, 03) > endpos <- c(02, 04) > typelist <- c('chr', 'num') > > startdata <- as.data.table(c('aa01', 'bb02')) > > enddata_want <- as.data.table(mapply(substr_typeswitch, startdata, > startpos, endpos, typelist)) > > If I examine enddata_want -- > >> str(enddata_want) > Classes ?data.table? and 'data.frame': 2 obs. of 2 variables: > $ V1: chr "aa" "bb" > $ NA: chr "1" "2" > - attr(*, ".internal.selfref")=<externalptr> > > "1" and "2" are being stored as character, and not as number.It appears from you code that you might be expecting a vector in a dataframe object to have a character mode in the first postition and a numeric mode in the second position. That wouldn't seem to be a reasonable expectation. But maybe you were hoping the chr and num types were to be applied to columns. I was surprised to get something different from as.data.table:> str(enddata_want)Classes ?data.table? and 'data.frame': 2 obs. of 2 variables: $ V1: Factor w/ 2 levels "aa","bb": 1 2 $ NA: Factor w/ 2 levels "1","2": 1 2 - attr(*, ".internal.selfref")=<externalptr> The mapply operation made a matrix which forces all values to be the same mode:> str( mapply(substr_typeswitch, startdata,+ startpos, endpos, typelist) ) chr [1:2, 1:2] "aa" "bb" "1" "2" - attr(*, "dimnames")=List of 2 ..$ : NULL ..$ : chr [1:2] "V1" NA You might have gotten something less homogeneous if you added the SIMPLIFY argument:> str( mapply(substr_typeswitch, startdata,+ startpos, endpos, typelist, SIMPLIFY=FALSE) ) List of 2 $ V1: chr [1:2] "aa" "bb" $ NA: num [1:2] 1 2> > Can anyone help me understand what I'm doing wrong? > > Thank you! > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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.David Winsemius Alameda, CA, USA
That's exactly what I wanted, thank you very much! My intent was to perform the SubStr operation first, and then apply the types to the columns. I wasn't expecting the two types in the same column. I appreciate your response! On Tue, Feb 10, 2015 at 5:03 PM, David Winsemius <dwinsemius at comcast.net> wrote:> > On Feb 10, 2015, at 3:58 PM, Brian Trautman wrote: > > > Hi! > > > > I'm trying to write a custom function that applies SubStr to a string, > and > > then depending on the arguments, converts the output to a number. > > > > The substring part of my code works fine, but it's not converting the > way I > > want to -- > > > > options('stringsAsFactors'=FALSE) > > require(data.table) > > > > substr_typeswitch <- function(x, start, stop, typeto='chr') > > { > > tmpvar <- substr(x=x, start=start, stop=stop) > > tmpvar <- switch(typeto, num=as.numeric(tmpvar), tmpvar) > > return(tmpvar) > > } > > startpos <- c(01, 03) > > endpos <- c(02, 04) > > typelist <- c('chr', 'num') > > > > startdata <- as.data.table(c('aa01', 'bb02')) > > > > enddata_want <- as.data.table(mapply(substr_typeswitch, startdata, > > startpos, endpos, typelist)) > > > > If I examine enddata_want -- > > > >> str(enddata_want) > > Classes ?data.table? and 'data.frame': 2 obs. of 2 variables: > > $ V1: chr "aa" "bb" > > $ NA: chr "1" "2" > > - attr(*, ".internal.selfref")=<externalptr> > > > > "1" and "2" are being stored as character, and not as number. > > It appears from you code that you might be expecting a vector in a > dataframe object to have a character mode in the first postition and a > numeric mode in the second position. That wouldn't seem to be a reasonable > expectation. But maybe you were hoping the chr and num types were to be > applied to columns. I was surprised to get something different from > as.data.table: > > > str(enddata_want) > Classes ?data.table? and 'data.frame': 2 obs. of 2 variables: > $ V1: Factor w/ 2 levels "aa","bb": 1 2 > $ NA: Factor w/ 2 levels "1","2": 1 2 > - attr(*, ".internal.selfref")=<externalptr> > > The mapply operation made a matrix which forces all values to be the same > mode: > > > str( mapply(substr_typeswitch, startdata, > + startpos, endpos, typelist) ) > chr [1:2, 1:2] "aa" "bb" "1" "2" > - attr(*, "dimnames")=List of 2 > ..$ : NULL > ..$ : chr [1:2] "V1" NA > > You might have gotten something less homogeneous if you added the SIMPLIFY > argument: > > > str( mapply(substr_typeswitch, startdata, > + startpos, endpos, typelist, SIMPLIFY=FALSE) ) > List of 2 > $ V1: chr [1:2] "aa" "bb" > $ NA: num [1:2] 1 2 > > > > > > > > Can anyone help me understand what I'm doing wrong? > > > > Thank you! > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help at 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. > > David Winsemius > Alameda, CA, USA > >[[alternative HTML version deleted]]