numeric_statistics/f64/
min.rs

1/// Calculate statistical min for values.
2///
3/// # Nan
4/// 
5/// Return NaN if the values are empty.
6///
7/// From <https://doc.rust-lang.org/std/primitive.f64.html#method.max>:
8///
9/// If one of the arguments is NaN, then the other argument is returned. This
10/// follows the IEEE 754-2008 semantics for minNum, except for handling of
11/// signaling NaNs; this function handles all NaNs the same way and avoids
12/// minNum’s problems with associativity. This also matches the behavior of
13/// libm’s fmin. In particular, if the inputs compare equal (such as for the case
14/// of +0.0 and -0.0), either input may be returned non-deterministically.
15///
16/// # Example
17///
18/// ```rust
19/// #[macro_use]
20/// use numeric_statistics::f64::min::*;
21/// let values = &[1.0, 2.0, 4.0];
22/// let min = min(values);
23/// assert_eq!(min, 1.0);
24/// ```
25/// 
26pub fn min<T: AsRef<[f64]>>(values: T) -> f64 {
27    let values = values.as_ref();
28    if values.is_empty() { return f64::NAN; }
29    values.iter().fold(f64::NAN, |a, x| f64::min(a, *x))
30}
31
32#[cfg(test)]
33mod test {
34    use super::*;
35
36    #[test]
37    fn test_empty() {
38        let x: &[f64] = &[];
39        assert!(min(x).is_nan());
40    }
41
42    #[test]
43    fn test_nan() {
44        let x: &[f64] = &[f64::NAN];
45        assert!(min(x).is_nan());
46    }
47
48    #[test]
49    fn test_value() {
50        let x: &[f64] = &[1.0];
51        assert_eq!(min(x), 1.0);
52    }
53
54    #[test]
55    fn test_values_ascending() {
56        let x = &[1.0, 2.0, 3.0];
57        assert_eq!(min(x), 1.0);
58    }
59
60    #[test]
61    fn test_values_ascending_and_nans() {
62        let x = &[1.0, f64::NAN, 2.0, f64::NAN, 3.0];
63        assert_eq!(min(x), 1.0);
64    }
65
66    #[test]
67    fn test_values_descending() {
68        let x = &[3.0, 2.0, 1.0];
69        assert_eq!(min(x), 1.0);
70    }
71
72        #[test]
73    fn test_values_descending_and_nans() {
74        let x = &[3.0, f64::NAN, 2.0, f64::NAN, 1.0];
75        assert_eq!(min(x), 1.0);
76    }
77
78}
numeric_statistics/f64/min.rs

numeric_statistics/f64/
min.rs
