Calculate threshold value on ranked input

Calculate a threshold value of a vector based on the unimodal threshold method described by Rosin 2001 for image thresholding. Conceptually, the method attempts to draw a line from the peak of the distribution to the tail and calculates the maximum distance from a point to that line. The point where the distance is maximized is the threshold.

Usage

rank_threshold(x, show = FALSE)

Arguments

x

numeric vector of values.

show_plot

logical. default (FALSE). Show the scatter plot for the given distribution.

Value

named vector containing "x" and "y" position of calculated threshold

Details

The function takes a numeric vector and ranks the values using data.table::frank. with ties.method = "first". The returned values for the threshold "x" and "y", indicate the rank of the data point and the value at that rank, respectively.

Examples

# simulate exponential counts
x <- (1:100)^exp(3)
rank_threshold(x, show = TRUE)

#>            x            y 
#> 8.500000e+01 5.667807e+38