Identify the inflection point for elbow-like data

This function will identify the index of the inflection point of an arbitrary series x ~ y via the biggest increase in the first derivative. Useful to identify key points in elbow plots.

Usage

get_inflection_point(x, y, span = 0.5)

Arguments

x, y

The x and y values.

span

The span parameter for the loess function.

Value

A list containing:

• inflection_idx - Index of the inflection point

• gradient_change - Absolute change in the first derivative

Examples

# elbow of a decaying curve that flattens out
x <- 1:20
y <- c(exp(-x[1:10] / 2), rep(0.005, 10))
get_inflection_point(x, y)$inflection_idx
#> [1] 3