Hi Dirk,
Thanks for your help. I am 99% confident that there is a better method to my
example below, but this is the only way i was able to pass the format string to
for the datetime object.
src<-'
StringVector stringVec(dates);
int n_stringVec=stringVec.size();
std::string fmt =Rcpp::as<std::string>( format );
DatetimeVector dateAll(n_stringVec);
std::string input;
for(int i=0;i<n_stringVec;i++){
input = stringVec[i];
Datetime dateTemp(input,fmt);
dateAll[i] = dateTemp;
}
return wrap(dateAll);
'
library(inline)
cpp_DatetimeVector<-cxxfunction(signature(dates="string",format="string"),src,plugin="Rcpp")
####Create a fictional dataset
foo<-seq(as.POSIXct("1960-01-01 00:00:00"),as.POSIXct("2010-01-01
00:00:00"),by='hour')
system.time(test<-cpp_DatetimeVector(foo,"%Y-%m-%d %H:%M:%OS"))
# user system elapsed
# 98.607 0.904 101.061
system.time(test2<-strptime(foo,"%Y-%m-%d %H:%M:%OS"))
# user system elapsed
# 14.089 0.261 14.501
On 19/05/2011, at 3:04 PM, Dirk Eddelbuettel wrote:
>
> Hi Jason,
>
> On 19 May 2011 at 11:00, Jason Lessels wrote:
> | Hi,
> | I have a very limited understanding of the class definition, but i was
> wondering if I could make a request for a minor change in relation to the two
> classes Datetime and the extension DatetimeVector. I have been successfully
> using Datetime class, passing both the date string and the format string, as
> this is allowed with the following definition;
> |
> | 00047 Datetime::Datetime(const std::string &s, const std::string
> &fmt) {
> | 00048 Rcpp::Function strptime("strptime"); // we cheat
> and call strptime() from R
> | 00049 Rcpp::Function asPOSIXct("as.POSIXct"); // and we
> need to convert to POSIXct
> | 00050 m_dt = Rcpp::as<double>(asPOSIXct(strptime(s, fmt)));
> | 00051 update_tm();
> | 00052 }
> |
> | however the DatetimeVector definition uses;
> |
> | 00027 DatetimeVector::DatetimeVector(SEXP vec)
> throw(std::range_error) : v() {
> | 00028 int i;
> | 00029 if (!Rf_isNumeric(vec) || Rf_isMatrix(vec) ||
> Rf_isLogical(vec))
> | 00030 throw std::range_error("DatetimeVector:
> invalid numeric vector in constructor");
> | 00031 int len = Rf_length(vec);
> | 00032 if (len == 0)
> | 00033 throw std::range_error("DatetimeVector: null
> vector in constructor");
> | 00034 v.resize(len);
> | 00035 for (i = 0; i < len; i++)
> | 00036 v[i] = Datetime(
> static_cast<double>(REAL(vec)[i]));
> | 00037 }
> |
> |
> | where line 36 calls Datetime without the ability to provide the format.
> Would it be possible for this to be changed to allow the format of the
> Datetime string. Currently I have to either convert the date string in R, or
> use an additional loop to convert the format, which make this slower than
> using the standard methods in R.
> |
> | Sorry in advance if my understanding is incorrect.
>
> I fear you may be confused. To see what constructors are defined, see the
> corresponding class declaration in its header. For Datetime we get
>
> [...]
>
> class Datetime {
> public:
> Datetime();
> Datetime(SEXP s);
> Datetime(const double &dt); // from double, just like
> POSIXct
> Datetime(const std::string &s, const std::string &fmt="%Y-%m-%d
> %H:%M:%OS");
> Datetime(const Datetime ©);
>
> [...]
>
> implying that we can construct 'empty', from SEXP, from double, from string +
> string and lastly from an existing Datetime.
>
> Also, your second code quote is 'an existance proof' of the asked-for
> constructor: Had it now existed, the second quote would not have compiled.
>
> As for your performance issues: can you send a small mock-up example we can
> grind through benchmark() or other timing tools?
>
> Dirk
>
> --
> Gauss once played himself in a zero-sum game and won $50.
> -- #11 at http://www.gaussfacts.com
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