[Rd] best methods for strings and structures?

Thomas Lumley tlumley at u.washington.edu
Wed Mar 17 01:30:21 MET 2004

On Tue, 16 Mar 2004, Jeff D. Hamann wrote:
>    PROTECT( ret_val = allocVector( VECSXP, 13 ) );
>    SET_STRING_ELT( ret_val, 0, mkChar( cfg_rec.coeffs_filename) );
>    SET_STRING_ELT( ret_val, 1, mkChar( cfg_rec.species_filename) );
>    SET_VECTOR_ELT( ret_val, 2, ScalarInteger( cfg_rec.use_random_error ) );

> The resulting list contains :
> > cfg
> $"coeffs_filename"
> <CHARSXP: "coeffs.txt">
> $"species_filename"
> <CHARSXP: "species.txt">
> $"use_random_error"
> [1] 1

> which seems to be acceptable, except for the two string at the beginning of
> the list. I'm not sure the best method to return string in the return vector
> and would like some advice on the best method to perform these operations.

You need the first two elements of the list to be vectors of character
objects, not character objects (just as the third element is a vector of
integers rather than a single integer.
Something like

SET_STRING_ELT(tempstr,0, mkChar( cfg_rec.coeffs_filename));
SET_VECTOR_ELT(ret_val,0, tempstr);
UNPROTECT(1);  /* tempstr */

(there may be more elegant versions of this).


Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

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