[Rcpp-devel] trouble creating a dataframe
Pratibha Rana
pratibha.r.tomar at gmail.com
Tue Jun 5 16:32:18 CEST 2012
I tried the code that you suggested on The R prompt and it worked as
expected. However the same piece of code doesn't work in my C++ app.
try{
IntegerVector v = IntegerVector::create(1,2,3);
std::vector<std::string> s(3);
s[0] = "a";
s[1] = "a";
s[2] = "a";
DataFrame df = DataFrame::create(Named("a")=v, Named("b")=s);
return df;
}
catch(std::exception &e) {
throw;
}
again I get
(gdb) p R_PV(df)
$1 = 0
On Mon, Jun 4, 2012 at 6:02 PM, Dirk Eddelbuettel <edd at debian.org> wrote:
>
> On 4 June 2012 at 17:28, Pratibha Rana wrote:
> | Something seems to go wrong in Vector_create::create__dispatch.
> |
> | (gdb) p t1
> | $14 = (const
> Rcpp::traits::named_object<std::vector<std::basic_string<char,
> | std::char_traits<char>, std::allocator<char> >, std::allocator
> | <std::basic_string<char, std::char_traits<char>, std::allocator<char> >
> > > >
> | &) @0x7fff5d321780: {name = "datatype", object = std::vector of length 2,
> | capacity 2 = {"varchar", "varchar"}}
> |
> | (gdb) p t2
> | $18 = (const Rcpp::traits::named_object<std::vector<int,
> std::allocator<int> >
> | > &) @0x7fff5d321760: {name = "length", object = std::vector of length 2,
> | capacity 2 = {10, 10}}
> |
> | (gdb) p t3
> | $19 = (const Rcpp::traits::named_object<std::vector<int,
> std::allocator<int> >
> | > &) @0x7fff5d321740: {name = "scale", object = std::vector of length 2,
> | capacity 2 = {0, 0}}
> |
> | (gdb) p res
> | $17 = {<Rcpp::RObject> = {<No data fields>}, <Rcpp::VectorBase<19, true,
> | Rcpp::Vector<19> >> = {<Rcpp::traits::expands_to_logical__impl<19>> =
> {<No data
> | fields>}, <No data fields>}, <Rcpp::internal::eval_methods<19>> = {<No
> data
> | fields>}, cache = {<Rcpp::traits::proxy_cache<19>> = {p = 0x0}, <No data
> | fields>}}
> |
> |
> | The value of res was printed at line 159 in Vector__create.h . Using
> Wrap()
> | makes it worse. I really need help. I have been trying to do this for 2
> days
> | now.
>
> What about the working example I just to the list?
>
> What about the following adapted from the unit test file for dataframes:
>
>
> R> library(inline)
> R>
> R> fx <- cxxfunction(signature(), plugin="Rcpp", body='
> + IntegerVector v = IntegerVector::create(1,2,3);
> + std::vector<std::string> s(3);
> + s[0] = "a";
> + s[1] = "b";
> + s[2] = "c";
> + return DataFrame::create(Named("a")=v, Named("b")=s);
> + ')
> R>
> R> fx()
> a b
> 1 1 a
> 2 2 b
> 3 3 c
> R>
>
>
> I usually start from self-contained working examples and then try to
> generalise to the specific issue at hand.
>
> Hope this helps, Dirk
>
>
> | On Mon, Jun 4, 2012 at 4:58 PM, Dirk Eddelbuettel <edd at debian.org>
> wrote:
> |
> |
> | Hi Pratibha,
> |
> | On 4 June 2012 at 16:12, Pratibha Rana wrote:
> | | I am at my wits end trying to create a dataframe from a list of
> values
> | that I
> | | have. here's the code
> | |
> | | try{
> | | int size = argTypes.getColumnCount();
> | | std::vector<std::string> nameVec(size);
> | | std::vector<int> lenVec(size);
> | | std::vector<int> scaleVec(size);
> |
> | Good. Three STL vectors which should get autmatic conversion via
> wrap().
> |
> | [...]
> |
> | | //create the dataframe
> | | Rcpp::List df = Rcpp::List::create(Rcpp::Named
> | ("datatype",nameVec),
> | |
> | Rcpp::Named("length",lenVec),
> | |
> | Rcpp::Named("scale",scaleVec));
> | | Rcpp::DataFrame df_final = Rcpp::DataFrame::create(df);
> | | return df_final;
> |
> | [...]
> |
> | | The std::vectors are created fine but the list is not created
> | | (gdb) p R_PV(df)
> | | $3 = 0
> | |
> | |
> | | I have tried a lot of variation like creating the dataframe
> directly
> | without
> | | first creating the list. Nothing seems to be working.
> |
> | It should work. I believe we posted example on the list, blog,
> possibly in
> | RcppExamples, ...
> |
> |
> | In fact, the latter one may be the best key. Consider this example
> taken
> | straight from the RcppExamples packages (which never became "the"
> | collection
> | of examples [ contributions welcome ] but has this ...)
> |
> | RcppExport SEXP RcppDataFrame(SEXP Dsexp) {
> |
> | try { // or
> | use BEGIN_RCPP macro
> |
> | // construct the data.frame object
> | Rcpp::DataFrame DF = Rcpp::DataFrame(Dsexp);
> |
> | // and access each column by name
> | Rcpp::IntegerVector a = DF["a"];
> | Rcpp::CharacterVector b = DF["b"];
> | Rcpp::DateVector c = DF["c"];
> |
> | // do something
> | a[2] = 42;
> | b[1] = "foo";
> | c[0] = c[0] + 7; // move up a week
> |
> | // create a new data frame
> | Rcpp::DataFrame NDF =
> | Rcpp::DataFrame::create(Rcpp::Named("a")=a,
> | Rcpp::Named("b")=b,
> | Rcpp::Named("c")=c);
> |
> | // and return old and new in list
> | return(Rcpp::List::create(Rcpp::Named("origDataFrame")=DF,
> | Rcpp::Named("newDataFrame")=
> | NDF));
> |
> | } catch( std::exception &ex ) { // or use END_RCPP
> | macro
> | forward_exception_to_r( ex );
> | } catch(...) {
> | ::Rf_error( "c++ exception (unknown reason)" );
> | }
> | return R_NilValue; // -Wall
> | }
> |
> |
> | The main difference is that we use Rcpp vectors. So you could try
> |
> | -- wrap() in the create() call
> | -- converting the Rcpp vectors to STL vectors
> | -- debugging why STL vectors don't pass through
> |
> | Please keep the list posted on your progress.
> |
> | Dirk
> |
> | --
> | Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
> |
> |
> |
> | ----------------------------------------------------------------------
> | _______________________________________________
> | Rcpp-devel mailing list
> | Rcpp-devel at lists.r-forge.r-project.org
> | https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
> --
> Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
>
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