From 5656156660a3cad9a036f37ab9fdf110c8985aac Mon Sep 17 00:00:00 2001
From: Vinzent Steinberg <Vinzent.Steinberg@gmail.com>
Date: Sun, 19 Nov 2017 10:31:00 +0100
Subject: [PATCH] Fix a negative underflow when calculating quantiles

Fixes #5.
---
 src/quantile.rs | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/quantile.rs b/src/quantile.rs
index 6d52631..8b59ae1 100644
--- a/src/quantile.rs
+++ b/src/quantile.rs
@@ -60,9 +60,9 @@ impl Quantile {
     #[inline]
     fn linear(&self, i: usize, d: f64) -> f64 {
         debug_assert_eq!(d.abs(), 1.);
-        let s: usize = d.approx().unwrap();
-        self.q[i] + d * (self.q[i + s] - self.q[i])
-            / f64::approx_from(self.n[i + s] - self.n[i]).unwrap()
+        let sum = if d < 0. { i - 1 } else { i + 1 };
+        self.q[i] + d * (self.q[sum] - self.q[i])
+            / f64::approx_from(self.n[sum] - self.n[i]).unwrap()
     }
 
     /// Estimate the p-quantile of the population.