Lerp function in base R?

[selkamand]

Is there a base R function that lerps between two numbers?

i.e. a function that would let you ask 'whats the number 50% between 10 and 20 and would return 15

Basically an inbuilt version of this:

lerp <- function(num1, num2, fraction){
  (num2-num1)*fraction+num1
}

[technocrat]

median(c(10,20))
#> [1] 15

[selkamand]

Apologies for the lack of clarity. I meant is there an inbuilt function that would take any fraction, and return the appropriate number? (not just 50%)

[technocrat]

Lack of clarity was on my end—focusing on the answer to the example, not the question.

I haven't been able to find a function in base that does this.

[Yarnabrina]

Genralise median to quantile, and it'll solve your question.

lerp <- function(num1, num2, fraction){
  (num2-num1)*fraction+num1
}

for (i in seq(0, 1, 0.01))
{
    a <- lerp(10, 20, i)
    b <- quantile(c(10, 20), i)
    if (isFALSE(all.equal(a, b))) {
        print(c(i, a, b))
    }
}

But nothing's wrong your function, as far as I can see. You can continue to use that as well.

[nirgrahamuk]

hacky but...

nums <- c(10,23)
f <- .65

lerp <- function(num1, num2, fraction){
  (num2-num1)*fraction+num1}
lerp(nums[1],nums[2],f)


approx(1:2,
       nums,
       n = 3,
       f = f,
       method = "constant")$y[[2]]

[Scoco]

Seconding the nomination of quantile, so the one-line answer to the OQ is quantile(c(num1,num2), fraction) will give the right answer.