| use crate::stats::float::Float; |
| use cast::{self, usize}; |
| |
| /// A "view" into the percentiles of a sample |
| pub struct Percentiles<A>(Box<[A]>) |
| where |
| A: Float; |
| |
| // TODO(rust-lang/rfcs#735) move this `impl` into a private percentiles module |
| impl<A> Percentiles<A> |
| where |
| A: Float, |
| usize: cast::From<A, Output = Result<usize, cast::Error>>, |
| { |
| /// Returns the percentile at `p`% |
| /// |
| /// Safety: |
| /// |
| /// - Make sure that `p` is in the range `[0, 100]` |
| unsafe fn at_unchecked(&self, p: A) -> A { |
| let _100 = A::cast(100); |
| debug_assert!(p >= A::cast(0) && p <= _100); |
| debug_assert!(self.0.len() > 0); |
| let len = self.0.len() - 1; |
| |
| if p == _100 { |
| self.0[len] |
| } else { |
| let rank = (p / _100) * A::cast(len); |
| let integer = rank.floor(); |
| let fraction = rank - integer; |
| let n = usize(integer).unwrap(); |
| let &floor = self.0.get_unchecked(n); |
| let &ceiling = self.0.get_unchecked(n + 1); |
| |
| floor + (ceiling - floor) * fraction |
| } |
| } |
| |
| /// Returns the percentile at `p`% |
| /// |
| /// # Panics |
| /// |
| /// Panics if `p` is outside the closed `[0, 100]` range |
| pub fn at(&self, p: A) -> A { |
| let _0 = A::cast(0); |
| let _100 = A::cast(100); |
| |
| assert!(p >= _0 && p <= _100); |
| assert!(self.0.len() > 0); |
| |
| unsafe { self.at_unchecked(p) } |
| } |
| |
| /// Returns the interquartile range |
| pub fn iqr(&self) -> A { |
| let q1 = self.at(A::cast(25)); |
| let q3 = self.at(A::cast(75)); |
| |
| q3 - q1 |
| } |
| |
| /// Returns the 50th percentile |
| pub fn median(&self) -> A { |
| self.at(A::cast(50)) |
| } |
| |
| /// Returns the 25th, 50th and 75th percentiles |
| pub fn quartiles(&self) -> (A, A, A) { |
| ( |
| self.at(A::cast(25)), |
| self.at(A::cast(50)), |
| self.at(A::cast(75)), |
| ) |
| } |
| } |