box-plotters 0.1.0

An alternative to the Boxplot and Quartiles types found in plotters
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152

use itertools::Itertools;

/// Stores the whisker positions, quartiles and median.
#[derive(Clone, Copy, Debug)]
pub struct Quartiles {
    pub lower_whisker: f64,
    pub lower_quartile: f64,
    pub median: f64,
    pub upper_quartile: f64,
    pub upper_whisker: f64,
}

impl Quartiles {
    /// Constructs a new [Quartiles] instance.
    pub fn new(
        lower_whisker: f64,
        lower_quartile: f64,
        median: f64,
        upper_quartile: f64,
        upper_whisker: f64,
    ) -> Self {
        Self { 
            lower_whisker, 
            lower_quartile, 
            median, 
            upper_quartile, 
            upper_whisker 
        }
    }

    /// Constructs a new [Quartiles] instance 
    /// where whiskers are calculated as the minimum and maximum value.
    /// Use [Quartiles::new_min_max_from_sorted] if the data is already sorted.
    pub fn new_min_max(values: &[f64]) -> Self {
        let sorted_values = values
            .iter()
            .cloned()
            .sorted_by(f64::total_cmp)
            .collect::<Vec<_>>();
        Self::new_min_max_from_sorted(&sorted_values)
    }

    /// Constructs a new [Quartiles] instance
    /// where whiskers are calculated as the minimum and maximum value.
    pub fn new_min_max_from_sorted(values: &[f64]) -> Self {
        let lower_whisker = quartile_from_sorted(values, 0.0);
        let lower_quartile = quartile_from_sorted(values, 1.0 / 4.0);
        let median = quartile_from_sorted(values, 1.0 / 2.0);
        let upper_quartile = quartile_from_sorted(values, 3.0 / 4.0);
        let upper_whisker = quartile_from_sorted(values, 1.0);
        Self::new(lower_whisker, lower_quartile, median, upper_quartile, upper_whisker)
    }

    /// Constructs a new [Quartiles] instance
    /// where whiskers are calculated using interquartile range
    /// (https://en.wikipedia.org/wiki/Interquartile_range).
    /// Use [Quartiles::new_iqr_from_sorted] if the data is already sorted.
    pub fn new_iqr(values: &[f64]) -> Self {
        let sorted_values = values
            .iter()
            .cloned()
            .sorted_by(f64::total_cmp)
            .collect::<Vec<_>>();
        Self::new_iqr_from_sorted(&sorted_values)
    }

    /// Constructs a new [Quartiles] instance from sorted data.
    /// where whiskers are calculated using interquartile range
    /// (https://en.wikipedia.org/wiki/Interquartile_range).
    pub fn new_iqr_from_sorted(values: &[f64]) -> Self {
        let min = quartile_from_sorted(values, 0.0);
        let lower_quartile = quartile_from_sorted(values, 1.0 / 4.0);
        let median = quartile_from_sorted(values, 1.0 / 2.0);
        let upper_quartile = quartile_from_sorted(values, 3.0 / 4.0);
        let max = quartile_from_sorted(values, 1.0);
        let iqr = upper_quartile - lower_quartile;
        let lower_whisker = (lower_quartile - 1.5 * iqr).max(min);
        let upper_whisker = (upper_quartile + 1.5 * iqr).min(max);
        Self::new(lower_whisker, lower_quartile, median, upper_quartile, upper_whisker)
    }

    /// Returns the fields as an array.
    pub fn values(&self) -> [f64; 5] {
        [
            self.lower_whisker,
            self.lower_quartile,
            self.median,
            self.upper_quartile,
            self.upper_whisker
        ]
    }
}

fn quartile_from_sorted(values: &[f64], t: f64) -> f64 {
    let p = t * (values.len() - 1) as f64;
    let a = values[p.floor() as usize];
    let b = values[p.ceil() as usize];
    lerp(a, b, p - p.floor())
}

fn lerp(a: f64, b: f64, t: f64) -> f64 {
    a + (b - a) * t
}

#[cfg(test)]
mod tests {
    use approx::assert_abs_diff_eq;

    use super::*;

    #[test]
    #[should_panic]
    fn test_min_max_panic() {
        Quartiles::new_min_max(&[]);
    }

    #[test]
    #[should_panic]
    fn test_iqr_panic() {
        Quartiles::new_iqr(&[]);
    }

    #[test]
    fn test_0_and_1_min_max() {
        let quartiles = Quartiles::new_min_max_from_sorted(&[0.0, 1.0]);
        assert_abs_diff_eq!(quartiles.lower_whisker, 0.0);
        assert_abs_diff_eq!(quartiles.lower_quartile, 0.25);
        assert_abs_diff_eq!(quartiles.median, 0.5);
        assert_abs_diff_eq!(quartiles.upper_quartile, 0.75);
        assert_abs_diff_eq!(quartiles.upper_whisker, 1.0);
    }

    #[test]
    fn test_0_and_1_iqr() {
        let quartiles = Quartiles::new_iqr_from_sorted(&[0.0, 1.0]);
        assert_abs_diff_eq!(quartiles.lower_whisker, 0.0);
        assert_abs_diff_eq!(quartiles.lower_quartile, 0.25);
        assert_abs_diff_eq!(quartiles.median, 0.5);
        assert_abs_diff_eq!(quartiles.upper_quartile, 0.75);
        assert_abs_diff_eq!(quartiles.upper_whisker, 1.0);
    }

    #[test]
    fn test_iqr_5_points() {
        let quartiles = Quartiles::new_iqr_from_sorted(&[0.0, 0.4, 0.5, 0.6, 1.0]);
        assert_abs_diff_eq!(quartiles.lower_whisker, 0.1);
        assert_abs_diff_eq!(quartiles.lower_quartile, 0.4);
        assert_abs_diff_eq!(quartiles.median, 0.5);
        assert_abs_diff_eq!(quartiles.upper_quartile, 0.6);
        assert_abs_diff_eq!(quartiles.upper_whisker, 0.9);
    }
}