Harmonic mean
The harmonic mean is the reciprocal of the arithmetic mean of the reciprocal of the data. That is
$$ \text{harmonic_mean}(x) = 1 / \text{arithmetic_mean}(1 / x) $$
The harmonic mean is often used to average ratio data. You'll be using it on the price/earnings ratio of stocks in the Standard and Poor's 500 index, provided as std_and_poor500. Price/earnings ratio is a measure of how expensive a stock is.
The dplyr package is loaded.
Cet exercice fait partie du cours
Introduction to Writing Functions in R
Exercice interactif pratique
Essayez cet exercice en complétant cet exemple de code.
# Look at the Standard and Poor 500 data
glimpse(std_and_poor500)
# Write a function to calculate the reciprocal
___ <- ___ {
___
}