[Rcpp-devel] Copy rownames and colnames from a NumericMatrix to another NumericMatrix

[Florian Plaza Oñate]

Thanks for answering.

By
"It does change the default rownames and colnames of the NumericMatrix"
understand
"It does not change the default rownames and colnames of the returned
NumericMatrix."

Actually, I don't want to create a copy of the matrix.
I want to create a new matrix which as the same size as the original
one, the same rownames and the same colnames but not the same content.

I may clone the original matrix and reset his content after. Is clone as
fast as creating a new matrix?

Le 11/08/2015 13:19, Dirk Eddelbuettel a écrit :
>
> On 11 August 2015 at 12:30, Florian Plaza Oñate wrote:
> | Hi everyone,
> |
> | I am trying to copy the rownames and the colnames from a NumericMatrix
> | to another NumericMatrix by using Rcpp
> |
> | Here is my code:
> |
> | Rcpp::NumericMatrix copy(const Rcpp::NumericMatrix& m)
> | {
> |    Rcpp::NumericMatrix m2(num_genes, num_samples);
> |    Rcpp::rownames(m2) = Rcpp::rownames(m);
> |    Rcpp::colnames(m2) = Rcpp::colnames(m);
>
> If you want a full copy, try
>
>     Rcpp::NumericMatrix m2 = Rcpp::clone(m);
>
> as in
>
> R> cppFunction("NumericMatrix foo(NumericMatrix m) { return Rcpp::clone(m); }");
> R> m <- matrix(1:4,2,2,TRUE,list(c("a","b"), c("c", "d")))
> R> foo(m)
>    c d
> a 1 2
> b 3 4
> R>
>
> |    return m2;
> | }
> |
> | It does change the default rownames and colnames of the NumericMatrix.
> | Do you know how to do it?
>
> Now I am confused. You do want to change them or not?
>
> If you do _not_ use clone(), then m2 and m share the same underlying
> pointer.  This has been explained before: we use proxy objects which are more
> lightweight.  Distinct copies require clone().
>
> Dirk
>