Dealing with Conditional in R

Bonjour!

In our daily life, we often face a condition where we have to anticipate and prepare for more than one outcome that might happen as a result of something that we have done. In a programming world, this situation is called a conditional statement.  In R, there are two ways of how we can handle conditional statement: if-else and case-when.

A. if-else

if-else can be done in two different ways: using if-else statement and ifelse() function.

1. if-else statement
   
   R

   if (test_expression) { statement1 } else { statement2 }

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   if (test_expression) {    statement1 } else {    statement2 }

   
   Example:
   
   R

   if(x > 75){ print("pass") } else { print("fail") }

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   if(x > 75){    print("pass") } else {    print("fail") }

2. ifelse() function
   Usage:  ifelse(test_expression, x, y)
   Example:
   
   R

   > x = c(75,17,92,39) > ifelse(x > 75,"pass","fail") [1] "fail" "fail" "pass" "fail"

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   > x = c(75,17,92,39) > ifelse(x > 75,"pass","fail") [1] "fail"  "fail"  "pass" "fail"

If we want to do nothing with the else part, we can do something like:   ifelse(is.na(donors$age), summary(donors$age)['Mean'], donors$age)

B. case_when()

Can we have too many conditions that we have to anticipate, it’s less painful to use case_when().

Usage:  case_when(cond1 ~ do1, cond2 ~ do2, ....)

Example:

Well, that’s my post for this week. It’s short but hopefully useful.

See you in my next post.

Cheers,

@erikaris