middle {coursekata}

Find a percentage of a distribution

Description

Given a distribution, find which values lie in the upper, lower, or middle proportion of the distribution. Useful when you want to do something like shade in the middle 95% of a plot. This is a greedy operation, meaning that if the cutoff point is between two whole numbers the specified region will suck up the extra space. For example, the requesting the upper 30% of the ⁠[1 2 3 4]⁠ will return ⁠[FALSE FALSE TRUE TRUE]⁠ because the 30% was greedy.

Usage

middle(x, prop = 0.95, greedy = TRUE)

tails(x, prop = 0.95, greedy = TRUE)

lower(x, prop = 0.025, greedy = TRUE)

upper(x, prop = 0.025, greedy = TRUE)

Arguments

x

The distribution of values to check.

prop

The proportion of values to find.

greedy

Whether the function should be greedy, as per the description above.

Details

Note that NA values are ignored, i.e. they will always return FALSE.

Value

A logical vector indicating which values are in the specified region.

Examples

upper(1:10, .1)
lower(1:10, .2)
middle(1:10, .5)
tails(1:10, .5)

sampling_distribution <- do(1000) * mean(rnorm(100, 5, 10))
sampling_distribution %>%
  gf_histogram(~mean, data = sampling_distribution, fill = ~ middle(mean, .68)) %>%
  gf_refine(scale_fill_manual(values = c("blue", "coral")))