如@Frank所建议的,可以使用Rcpp
来实现这一功能。以下是一个版本,包含受Rcpp的dispatch.h
启发的宏,可处理所有原子向量类型:
mod_vector.cpp
#include <Rcpp.h>
using namespace Rcpp;
template <int RTYPE>
Vector<RTYPE> mod_vector_impl(Vector<RTYPE> x, IntegerVector i, Vector<RTYPE> value) {
if (i.size() != value.size()) {
stop("i and value must have same length.");
}
for (int a = 0; a < i.size(); a++) {
x[i[a] - 1] = value[a];
}
return x;
}
#define __MV_HANDLE_CASE__(__RTYPE__) case __RTYPE__ : return mod_vector_impl(Vector<__RTYPE__>(x), i, Vector<__RTYPE__>(value));
SEXP mod_vector(SEXP x, IntegerVector i, SEXP value) {
switch(TYPEOF(x)) {
__MV_HANDLE_CASE__(INTSXP)
__MV_HANDLE_CASE__(REALSXP)
__MV_HANDLE_CASE__(RAWSXP)
__MV_HANDLE_CASE__(LGLSXP)
__MV_HANDLE_CASE__(CPLXSXP)
__MV_HANDLE_CASE__(STRSXP)
__MV_HANDLE_CASE__(VECSXP)
__MV_HANDLE_CASE__(EXPRSXP)
}
stop("Not supported.");
return x;
}
例子:
x <- 1:20
address(x)
mod_vector(x, 4:5, 12:13)
address(x)
与基础和data.table方法的比较。可以看出,它要快得多:
x <- 1:2e7
microbenchmark::microbenchmark(mod_vector(x, 4:5, 12:13), x[4:5] <- 12:13, modify.vector(x, 4:5, 12:13))