geo 0.33.0

Geospatial primitives and algorithms
Documentation 
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use crate::CoordsIter;
use crate::GeoFloat;
use crate::algorithm::{Distance, Euclidean};
use geo_types::{Coord, Point};
use num_traits::Bounded;

/// Determine the distance between two geometries using the [Hausdorff distance formula].
///
/// Hausdorff distance is used to compare two point sets. It measures the maximum euclidean
/// distance of a point in one set to the nearest point in another set. Hausdorff distance
/// is often used to measure the amount of mismatch between two sets.
///
/// [Hausdorff distance formula]: https://en.wikipedia.org/wiki/Hausdorff_distance
pub trait HausdorffDistance<T>
where
    T: GeoFloat,
{
    fn hausdorff_distance<Rhs>(&self, rhs: &Rhs) -> T
    where
        Rhs: CoordsIter<Scalar = T>;
}

impl<T, G> HausdorffDistance<T> for G
where
    T: GeoFloat,
    G: CoordsIter<Scalar = T>,
{
    fn hausdorff_distance<Rhs>(&self, rhs: &Rhs) -> T
    where
        Rhs: CoordsIter<Scalar = T>,
    {
        // calculate from A -> B
        let hd1 = self
            .coords_iter()
            .map(|c| {
                rhs.coords_iter()
                    .map(|c2| Euclidean.distance(c, c2))
                    .fold(<T as Bounded>::max_value(), |accum, val| accum.min(val))
            })
            .fold(<T as Bounded>::min_value(), |accum, val| accum.max(val));

        // Calculate from B -> A
        let hd2 = rhs
            .coords_iter()
            .map(|c| {
                self.coords_iter()
                    .map(|c2| Euclidean.distance(c, c2))
                    .fold(<T as Bounded>::max_value(), |accum, val| accum.min(val))
            })
            .fold(<T as Bounded>::min_value(), |accum, val| accum.max(val));

        // The max of the two
        hd1.max(hd2)
    }
}

// ┌───────────────────────────┐
// │ Implementations for Coord │
// └───────────────────────────┘

impl<T> HausdorffDistance<T> for Coord<T>
where
    T: GeoFloat,
{
    fn hausdorff_distance<Rhs>(&self, rhs: &Rhs) -> T
    where
        Rhs: CoordsIter<Scalar = T>,
    {
        Point::from(*self).hausdorff_distance(rhs)
    }
}

#[cfg(test)]
mod test {
    use crate::HausdorffDistance;
    use crate::{MultiPoint, MultiPolygon, line_string, polygon};

    #[test]
    fn hd_mpnt_mpnt() {
        let p1: MultiPoint<_> = vec![(0., 0.), (1., 2.)].into();
        let p2: MultiPoint<_> = vec![(2., 3.), (1., 2.)].into();
        assert_relative_eq!(p1.hausdorff_distance(&p2), 2.236068, epsilon = 1.0e-6);
    }

    #[test]
    fn hd_mpnt_poly() {
        let p1: MultiPoint<_> = vec![(0., 0.), (1., 2.)].into();
        let poly = polygon![
        (x: 1., y: -3.1), (x: 3.7, y: 2.7),
        (x: 0.9, y: 7.6), (x: -4.8, y: 6.7),
        (x: -7.5, y: 0.9), (x: -4.7, y: -4.),
        (x: 1., y: -3.1)
        ];

        assert_relative_eq!(p1.hausdorff_distance(&poly), 7.553807, epsilon = 1.0e-6)
    }

    #[test]
    fn hd_mpnt_lns() {
        let p1: MultiPoint<_> = vec![(0., 0.), (1., 2.)].into();
        let lns = line_string![
        (x: 1., y: -3.1), (x: 3.7, y: 2.7),
        (x: 0.9, y: 7.6), (x: -4.8, y: 6.7),
        (x: -7.5, y: 0.9), (x: -4.7, y: -4.),
        (x: 1., y: -3.1)
        ];

        assert_relative_eq!(p1.hausdorff_distance(&lns), 7.553807, epsilon = 1.0e-6)
    }

    #[test]
    fn hd_mpnt_mply() {
        let p1: MultiPoint<_> = vec![(0., 0.), (1., 2.)].into();
        let multi_polygon = MultiPolygon::new(vec![
            polygon![
              (x: 0.0f32, y: 0.0),
              (x: 2.0, y: 0.0),
              (x: 2.0, y: 1.0),
              (x: 0.0, y: 1.0),
            ],
            polygon![
              (x: 1.0, y: 1.0),
              (x: -2.0, y: 1.0),
              (x: -2.0, y: -1.0),
              (x: 1.0, y: -1.0),
            ],
        ]);

        assert_relative_eq!(
            p1.hausdorff_distance(&multi_polygon),
            2.236068,
            epsilon = 1.0e-6
        )
    }
}