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Some sample Rcpp code
library(Rcpp)
# Simple addition
add_r <- function(x, y, z) {
sum = x + y + z
return(sum)
}
cppFunction(
"int add_c(int x, int y, int z) {
int sum = x + y + z;
return sum;
}")
add_r(1, 2, 3)
add_c(1, 2, 3)
# Euclidean distance
dist_r <- function(x, ys) {
sqrt((x - ys) ^ 2)
}
cppFunction(
"NumericVector dist_c(double x, NumericVector ys) {
int n = ys.size();
NumericVector out(n);
for(int i = 0; i < n; i++) {
out[i] = sqrt(pow(ys[i] - x, 2.0));
}
return out;
}")
dist_r(10, 20:25)
dist_c(10, 20:25)
# Summation with conditionals
sum_r <- function(v) {
total <- 0
for (e in v) {
if (e < 0) { total = total - e }
else if (e > 0.75) { total = total + e/2 }
else { total = total + e }
}
return(total)
}
cppFunction(
"double sum_c(NumericVector v) {
double total = 0;
for (int i = 0; i < v.size(); i++) {
if (v[i] < 0) { total -= v[i]; }
else if (v[i] > 0.75) { total += v[i]/2; }
else { total += v[i]; }
}
return(total);
}")
v <- runif(100000, -1, 1)
microbenchmark::microbenchmark(sum_r(v), sum_c(v))
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