CODEWITHSUNDEEP
r
S.P
S.P

Reputation: 37

Why am I receiving the error "Attempt to Apply Non-Function"

I have the following code:

pdf=function(x) {
  if (x<=1 && x>2) 0 
  else if (1.5>x && x>1) (4*(x-1))
  else (x>=1.5 && x<=2) (4*(2-x))
}

Where I'm attempting to create a function of a probability density function and calculating the density at x= 1.25, x=1.75, x=1.95. It runs through with no problem and calculates the first value of x=1.25. However, when attempting to calculate the values x=1.75 and x=1.95, it returns with the error message:

Error in (x >= 1.5 && x <= 2)(4 * (2 - x)) : attempt to apply non-function

Any help would be greatly appreciated.

I've already attempted to remove the brackets around (4*(x-1)) and (4*(2-x)), both don't solve the issue and the latter returns the error of an unexpected numeric constant.

Upvotes: 0

Views: 430

Answers (2)

Rui Barradas
Rui Barradas

Reputation: 76402

Here are two vectorized ways, one with ifelse, the other with logical indices.

pdf <- function(x) {
  ifelse(x <= 1 | x > 2, 0, 
         ifelse(1 < x & x < 1.5, 4*(x - 1), 4*(2 - x)
         )
  )
}

pdf2 <- function(x){
  i <- 1 < x & x < 1.5
  j <- 1.5 <= x & x <= 2
  y <- rep(0, length(x))
  y[i] <- 4*(x[i] - 1)
  y[j] <- 4*(2 - x[j])
  y
}

X <- seq(-1, 3, by = 0.1)
identical(pdf(X), pdf2(X))
#[1] TRUE

Upvotes: 0

Snel23
Snel23

Reputation: 1379

Your issue is, that else does not use a conditional statement, and is only ever executed if all other if statements are false.

You have to add an else if statement to your final else, so that the conditional is actually used.

Edit: As @Shree pointed out in the comments, your initial if statement will never be reached, and should be an OR operator rather than an AND

pdf=function(x) {
  if (x<=1 || x>2) 0 
  else if (1.5>x && x>1) (4*(x-1))
  else if (x>=1.5 && x<=2) (4*(2-x))
}

As pointed out by @Tim Biegeleisen in the comments, the final else if may not particularly be necessary, and you can do the following instead

pdf=function(x) {
  if (x<=1 || x>2) 0 
  else if (1.5>x && x>1) (4*(x-1))
  else (4*(2-x))
}

Upvotes: 3

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