mif2.c

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// -*- C++ -*-
 
#include "internal.h"
#include <Rdefines.h>
 
SEXP randwalk_perturbation (SEXP params, SEXP rw_sd)
{
  double *xp = 0, *rw, *xrw, *xs;
  SEXP Pnames, rwnames, pindex;
  int *dim, *pidx;
  int nrw = 0, npars, nreps;
  int j, k;
 
  PROTECT(params = duplicate(params));
 
  // unpack parameter matrix
  xp = REAL(params);
  dim = INTEGER(GET_DIM(params)); npars = dim[0]; nreps = dim[1];
  PROTECT(Pnames = GET_ROWNAMES(GET_DIMNAMES(params)));
 
  // names of parameters undergoing random walk
  PROTECT(rwnames = GET_NAMES(rw_sd));
  nrw = LENGTH(rwnames); rw = REAL(rw_sd);
 
  // indices of parameters undergoing random walk
  PROTECT(pindex = matchnames(Pnames,rwnames,"parameters"));
  pidx = INTEGER(pindex);
 
  GetRNGstate();
 
  for (j = 0, xrw = rw; j < nrw; j++, pidx++, xrw++) {
    for (k = 0, xs = xp+(*pidx); k < nreps; k++, xs += npars) {
      *xs += *xrw * norm_rand();
    }
  }
 
  PutRNGstate();
 
  UNPROTECT(4);
  return(params);
}
SEXP randwalk_perturbation (SEXP params, SEXP rw_sd) {…}