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

#[cfg(feature = "serde")]
use serdecrate::{Deserialize, Serialize};

#[cfg_attr(
    feature = "serde",
    derive(Serialize, Deserialize),
    serde(crate = "serdecrate")
)]
#[derive(Clone, Debug, PartialEq)]
/// The set of hyperparameters that can be specified for the execution of
/// the [DBSCAN algorithm](struct.Dbscan.html).
pub struct DbscanHyperParams {
    /// Distance between points for them to be considered neighbours.
    tolerance: f64,
    /// Minimum number of neighboring points a point needs to have to be a core
    /// point and not a noise point.
    min_points: usize,
}

/// Helper struct used to construct a set of hyperparameters for
pub struct DbscanHyperParamsBuilder {
    tolerance: f64,
    min_points: usize,
}

impl DbscanHyperParamsBuilder {
    /// Distance between points for them to be considered neighbours.
    pub fn tolerance(mut self, tolerance: f64) -> Self {
        self.tolerance = tolerance;
        self
    }

    /// Return an instance of `DbscanHyperParams` after having performed
    /// validation checks on all hyperparameters.
    ///
    /// **Panics** if any of the validation checks fail.
    pub fn build(self) -> DbscanHyperParams {
        DbscanHyperParams::build(self.tolerance, self.min_points)
    }
}

impl DbscanHyperParams {
    /// Minimum number of neighboring points a point needs to have to be a core
    /// point and not a noise point.
    ///
    /// Defaults are provided if the optional parameters are not specified:
    /// * `tolerance = 1e-4`
    // Violates the convention that new should return a value of type `Self`
    #[allow(clippy::new_ret_no_self)]
    pub fn new(min_points: usize) -> DbscanHyperParamsBuilder {
        DbscanHyperParamsBuilder {
            min_points,
            tolerance: 1e-4,
        }
    }

    /// Two points are considered neighbors if the euclidean distance between
    /// them is below the tolerance
    pub fn tolerance(&self) -> f64 {
        self.tolerance
    }

    /// Minimum number of a points in a neighborhood around a point for it to
    /// not be considered noise
    pub fn minimum_points(&self) -> usize {
        self.min_points
    }

    fn build(tolerance: f64, min_points: usize) -> Self {
        if tolerance <= 0. {
            panic!("`tolerance` must be greater than 0!");
        }
        // There is always at least one neighbor to a point (itself)
        if min_points <= 1 {
            panic!("`min_points` must be greater than 1!");
        }
        Self {
            tolerance,
            min_points,
        }
    }
}