I want to create functions that I can test with multiple inputs such as a list of numbers below is my code. I want to test several inputs not only but I do not how to do the same in the function argument.

grads<-function((for (X in 0:100)))
  
if (x<=50){
  "Fail"
}else if (x<=70){
  "Good"
  
}else if (x<=80){
  "V Good"
} else {
  "Execellent"
}

grads(95,60,77,33)

this is error that I got

Error in grads(95, 60, 77, 33) : unused arguments (60, 77, 33)

CodePudding user response：

We can use fcase from data.table

library(data.table)
grads <- function(x) {
     data.table::fcase(x <= 50, "Fail",
                       x <= 70, "Good",
                       x <= 80, "Very Good",
                       default = "Excellent")
}

-testing

grads(c(95,60,77,33))
[1] "Excellent" "Good"      "Very Good" "Fail"  

Or using findInterval from base R

grads <- function(x)  {
      c("Fail", "Good", "Very Good", "Excellent")[findInterval(x,
       c(0, 50, 70, 80, 100))]
}
grads(c(95,60,77,33))
[1] "Excellent" "Good"      "Very Good" "Fail"    

CodePudding user response：

You need to use vectorized functions to work with more than one value.

Here are some options.

1. Nested ifelse.

grads<- function(x) {
  ifelse(x <= 50, "Fail", 
         ifelse(x <= 70, "Good", 
                ifelse(x <= 80, "Very Good", "Excellent")))
}

grads(c(95,60,77,33))
#[1] "Excellent" "Good"      "Very Good" "Fail" 

2. case_when from dplyr which is more readable for nested conditions

grads<- function(x) {
  dplyr::case_when(x <= 50 ~ "Fail", 
                   x <= 70 ~ "Good", 
                   x <= 80 ~ "Very Good",
                   TRUE ~ "Excellent")
}
grads(c(95,60,77,33))

3. cut which is scalable.

grads<- function(x) {
  cut(x, c(0, 50, 70, 80, 100), c("Fail", "Good", "Very Good", "Excellent"))
}
grads(c(95,60,77,33))