1. Apprendre
    2. /
  2. Cours
    3. /
  3. Optimizing R Code with Rcpp
  • 1

    Introduction

    Gratuit

    Writing, benchmarking, and debugging your first C++ code.

  • 2

    Functions and Control Flow

    Writing functions, controlling the flow with if and else, and learning to use the three kinds of loops in C++.

  • 3

    Vector classes

    Manipulate and compute with Rcpp and native C++ vectors.

  • 4

    Case Studies

    Use random numbers and write algorithms for applied time series models.

Initializing

Exercice

Handling of missing values

In R, to test for a missing value you must use is.na(x). (What happens if you try x == NA?)

The equivalent in Rcpp is the static method is_na(). Recall that static means the method is part of the class, not the particular variable. For example, NumericVector::is_na(x) tests if the double x is a missing value.
Similarly, the static method get_na() gives you the NA for the associated class. For example, CharacterVector::get_na() returns a missing character value.

Note that the logical or in C++ is the same as in R, ||.

Instructions

100 XP
  • Update the weighted_mean_cpp() function from the previous exercise so that it returns a missing value as soon as a missing value is seen on x or w.
    • Add an if block that checks if the ith element of x is NA or the ith element of w is NA.
    • Inside that if block, return a numeric NA.