std: add stats.

Author: graydon

src/libstd/stats.rs

@@ -0,0 +1,96 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use core::vec;
+use core::f64;
+use core::cmp;
+use core::num;
+use sort;
+
+// NB: this can probably be rewritten in terms of num::Num
+// to be less f64-specific.
+
+pub trait Stats {
+    fn sum(self) -> f64;
+    fn min(self) -> f64;
+    fn max(self) -> f64;
+    fn mean(self) -> f64;
+    fn median(self) -> f64;
+    fn var(self) -> f64;
+    fn std_dev(self) -> f64;
+    fn std_dev_pct(self) -> f64;
+    fn median_abs_dev(self) -> f64;
+    fn median_abs_dev_pct(self) -> f64;
+}
+
+impl &[f64] : Stats {
+    fn sum(self) -> f64 {
+        vec::foldl(0.0, self, |p,q| p + *q)
+    }
+
+    fn min(self) -> f64 {
+        assert self.len() != 0;
+        vec::foldl(self[0], self, |p,q| cmp::min(p, *q))
+    }
+
+    fn max(self) -> f64 {
+        assert self.len() != 0;
+        vec::foldl(self[0], self, |p,q| cmp::max(p, *q))
+    }
+
+    fn mean(self) -> f64 {
+        assert self.len() != 0;
+        self.sum() / (self.len() as f64)
+    }
+
+    fn median(self) -> f64 {
+        assert self.len() != 0;
+        let tmp = vec::to_mut(vec::from_slice(self));
+        sort::tim_sort(tmp);
+        if tmp.len() & 1 == 0 {
+            let m = tmp.len() / 2;
+            (tmp[m] + tmp[m-1]) / 2.0
+        } else {
+            tmp[tmp.len() / 2]
+        }
+    }
+
+    fn var(self) -> f64 {
+        if self.len() == 0 {
+            0.0
+        } else {
+            let mean = self.mean();
+            let mut v = 0.0;
+            for self.each |s| {
+                let x = *s - mean;
+                v += x*x;
+            }
+            v/(self.len() as f64)
+        }
+    }
+
+    fn std_dev(self) -> f64 {
+        f64::sqrt(self.var())
+    }
+
+    fn std_dev_pct(self) -> f64 {
+        (self.std_dev() / self.mean()) * 100.0
+    }
+
+    fn median_abs_dev(self) -> f64 {
+        let med = self.median();
+        let abs_devs = self.map(|v| num::abs(med - *v));
+        abs_devs.median()
+    }
+
+    fn median_abs_dev_pct(self) -> f64 {
+        (self.median_abs_dev() / self.median()) * 100.0
+    }
+}

src/libstd/std.rc

@@ -98,6 +98,7 @@ pub mod base64;
 pub mod rl;
 pub mod workcache;
 pub mod bigint;
+pub mod stats;
 
 #[cfg(unicode)]
 mod unicode;