Search code examples
rfunctiondataframepercentagesummary

Write Function to Calculate Percentage and Place it in a New Column of the Data Frame

I have a data frame where an athlete receives a performance rating of "Good", "Fair" and "Poor".

I would like to write a function that does the following:

Produces a new data frame that contains The name of the athlete The percentage of times the athlete received a "Good" rating

Player <- c("Jordan", "Jordan", "Jordan", "Jordan", "Jordan", "Jordan", 
"Jordan","Jordan","Jordan", "Barkley", "Barkley", "Barkley", "Barkley", 
"Barkley", "Olajuwon", "Olajuwon", "Olajuwon", "Olajuwon", "Olajuwon", 
"Kemp", "Kemp", "Kemp", "Kemp", "Kemp", "Kemp")

Rating <- c("Good", "Fair", "Good", "Good", "Good", "Poor", "Good", "Good",  
"Good", "Fair", "Fair", "Poor", "Good", "Good", "Good", "Fair", "Good", 
"Fair", "Good", "Good", "Good", "Good", "Good", "Good", "Poor")

df <- data.frame(Player, Rating)

I would want output that is:

Player    PercentGood
Jordan    77.8%
Barkley   40.0%
Olajuwon  60.0%
Kemp      83.3%

When I receive the file the percent is not included so I want to run this each time an updated file is sent to me.

So the file is sent, I apply code and a new data frame is produced that gives me a summary of the percentage that an athlete received a rating of "Good"

Thank you.

Solution

  • Here's a tidyverse solution using scales::percent to format for percentage.

    It first makes a new variable good or not encoded as 1 or 0. Then the percentage of 1s is calculated for each player.

    library(tidyverse)
library(scales)
df %>% mutate(good = ifelse(Rating == "Good", 1, 0)) %>% 
  group_by(Player = fct_inorder(Player)) %>% 
  summarise(PercentGood = percent(mean(good)))

# A tibble: 4 x 2
#  Player   PercentGood
#  <fct>    <chr>  
#1 Jordan   77.8%  
#2 Barkley  40.0%  
#3 Olajuwon 60.0%  
#4 Kemp     83.3%