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

use linfa::param_guard::TransformGuard;
use linfa::prelude::*;
use linfa::Float;

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

#[cfg_attr(
    feature = "serde",
    derive(Serialize, Deserialize),
    serde(crate = "serde_crate")
)]
#[derive(Clone, Debug, PartialEq)]
/// The set of hyperparameters that can be specified for the execution of
/// the [Approximated DBSCAN algorithm](struct.AppxDbscan.html).
pub struct AppxDbscanValidParams<F: Float> {
    pub(crate) tolerance: F,
    pub(crate) min_points: usize,
    pub(crate) slack: F,
}

#[derive(Debug)]
/// Helper struct for building a set of [Approximated DBSCAN
/// hyperparameters](struct.AppxDbscanParams.html)
pub struct AppxDbscanParams<F: Float>(AppxDbscanValidParams<F>);

#[derive(Debug, Error)]
pub enum AppxDbscanParamsError {
    #[error("tolerance must be greater than 0")]
    Tolerance,
    #[error("min_points must be greater than 1")]
    MinPoints,
    #[error("slack must be greater than 0")]
    Slack,
}

impl<F: Float> AppxDbscanParams<F> {
    pub(crate) fn new(min_points: usize) -> Self {
        let default_slack = F::cast(1e-2);
        let default_tolerance = F::cast(1e-4);

        Self(AppxDbscanValidParams {
            min_points,
            tolerance: default_tolerance,
            slack: default_slack,
        })
    }

    /// Set the tolerance
    pub fn tolerance(mut self, tolerance: F) -> Self {
        self.0.tolerance = tolerance;
        self
    }

    /// Set the slack
    pub fn slack(mut self, slack: F) -> Self {
        self.0.slack = slack;
        self
    }
}

impl<F: Float> ParamGuard for AppxDbscanParams<F> {
    type Checked = AppxDbscanValidParams<F>;
    type Error = AppxDbscanParamsError;

    fn check_ref(&self) -> Result<&Self::Checked, Self::Error> {
        if self.0.min_points <= 1 {
            Err(AppxDbscanParamsError::MinPoints)
        } else if self.0.tolerance <= F::zero() {
            Err(AppxDbscanParamsError::Tolerance)
        } else if self.0.slack <= F::zero() {
            Err(AppxDbscanParamsError::Slack)
        } else {
            Ok(&self.0)
        }
    }

    fn check(self) -> Result<Self::Checked, Self::Error> {
        self.check_ref()?;
        Ok(self.0)
    }
}
impl<F: Float> TransformGuard for AppxDbscanParams<F> {}

impl<F: Float> AppxDbscanValidParams<F> {
    /// Distance between points for them to be considered neighbours.
    pub fn tolerance(&self) -> F {
        self.tolerance
    }

    /// Distance between points for them to be considered neighbours.
    pub fn minimum_points(&self) -> usize {
        self.min_points
    }

    /// Minimum number of neighboring points a point needs to have to be a core
    /// point and not a noise point.
    pub fn slack(&self) -> F {
        self.slack
    }

    /// Get the approximate tolerance (`tolerance * (1 + slack)`)
    /// Approximation factor, allows the distance between two points
    /// for them to be considered neighbours to reach
    /// `tolerance * (1 + slack)`
    pub fn appx_tolerance(&self) -> F {
        self.tolerance * (F::one() + self.slack)
    }
}