scale.hpp

[SymbolixAU]

The performance of range() can be improved.

## benchmarking numbers vs categories
n <- 1e7
x <- rnorm(n = n)

library(stringi)
y <- do.call(paste0, Map(stri_rand_strings, n=n, length=c(5, 4, 1),
                         pattern = c('[A-Z]', '[0-9]', '[A-Z]')))


library(microbenchmark)

microbenchmark(
  numeric = { v1 <- colourvalues::colour_values( x ) },
  character = { v2 <- colourvalues::colour_values( y ) },
  times = 5
)


library(Rcpp)

cppFunction('Rcpp::NumericVector range_sort( Rcpp::NumericVector x) {
  //NumericVector y = clone(x);
  int n = x.size() - 1;
  std::sort(x.begin(), x.end());
  Rcpp::NumericVector rng(2);
  rng[0] = x[0];
  rng[1] = x[n];
  return rng;
}')

cppFunction('Rcpp::NumericVector range_min_max( Rcpp::NumericVector x) {
  //NumericVector y = clone(x);
  Rcpp::NumericVector rng(2);
  rng[0] = min( na_omit(x) );
  rng[1] = max( na_omit(x) );
  return rng;
}')

cppFunction('Rcpp::NumericVector for_min_max( Rcpp::NumericVector x ) {
  //NumericVector y = clone(x);
  int n = x.size();

  double min;
  double max;
  bool first_value = false;

  for( int i = 0; i < n; i++) {

    if( !ISNAN( x[i] ) ) {
      if( !first_value ) {
        min = x[i];
        max = x[i];
        first_value = true;
      } else {
        if( x[i] < min ) {
          min = x[i];
        } else if ( x[i] > max) {
          max = x[i];
        }
      }
    }
  }
  return NumericVector::create(min, max);
}')

cppFunction('Rcpp::NumericVector rng( Rcpp::NumericVector x) {
  NumericVector y = clone(x);
  return range(x);
}')

for_min_max(1:20)
rng(1:20)

n <- 1e7
x <- rnorm(n = n)

microbenchmark(
  range_sort = { range_sort( x ) },
  range_min_max = { range_min_max( x ) },
  for_min_max = { for_min_max( x ) },
  rng = { rng( x ) },
  times = 25
)

# Unit: milliseconds
#          expr      min       lq     mean   median       uq      max neval
#    range_sort 10.59129 11.61915 12.53094 12.47773 13.46021 14.14382    25
# range_min_max 78.81943 79.62402 83.29948 83.36582 85.20105 90.31657    25
#   for_min_max 33.78131 34.10332 35.19830 35.19227 35.75790 37.37187    25
#           rng 43.45526 46.92417 48.55556 48.48253 49.81096 53.31669    25

TODO

• implement for_min_max

(std::sort doesn't handle NAs (inside range_sort()))