window.cpp

#include <Rcpp.h>
using namespace Rcpp;

//' Cumulativate versions of any, all, and mean
//'
//' dplyr adds \code{cumall}, \code{cumany}, and \code{cummean} to complete
//' R's set of cumulate functions to match the aggregation functions available
//' in most databases
//'
//' @param x For \code{cumall} & \code{cumany}, a logical vector; for
//'   \code{cummean} an integer or numeric vector
//' @export
// [[Rcpp::export]]
LogicalVector cumall(LogicalVector x) {
  int n = x.length();
  LogicalVector out(n, NA_LOGICAL);

  int current = out[0] = x[0];
  if( current == NA_LOGICAL) return out ;
  if( current == FALSE){
    std::fill( out.begin(), out.end(), FALSE ) ;
    return out ;
  }
  for (int i = 1; i < n; i++) {
    current = x[i] ;
    if( current == NA_LOGICAL ) break ;
    if( current == FALSE ){
      std::fill( out.begin() + i, out.end(), FALSE ) ;
      break ;
    }
    out[i] = current && out[i - 1];
  }
  return out;
}

//' @export
//' @rdname cumall
// [[Rcpp::export]]
LogicalVector cumany(LogicalVector x) {
  int n = x.length();
  LogicalVector out(n, NA_LOGICAL);

  int current = out[0] = x[0];
  if( current == NA_LOGICAL ) return out ;
  if( current == TRUE ){
    std::fill( out.begin(), out.end(), TRUE ) ;
    return out ;
  }
  for (int i = 1; i < n; i++) {
    current = x[i] ;
    if( current == NA_LOGICAL ) break ;
    if( current == TRUE ){
      std::fill( out.begin() + i, out.end(), TRUE ) ;
      break ;
    }
    out[i] = current || out[i - 1];
  }

  return out;
}

//' @export
//' @rdname cumall
// [[Rcpp::export]]
NumericVector cummean(NumericVector x) {
  int n = x.length();
  NumericVector out = no_init(n);

  double sum = out[0] = x[0];
  for (int i = 1; i < n; i++ ) {
    sum += x[i];
    out[i] = sum / (i + 1.0);
  }

  return out;
}