h3ron 0.18.0

High-level rust API for H3
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

use crate::collections::HashMap;
use crate::iter::GridDiskBuilder;
use crate::{Error, H3Cell};
use ahash::RandomState;
use hashbrown::hash_map::Entry;
use indexmap::IndexMap;
use std::cmp::Ordering;

/// find clusters of neighboring cells
///
/// Requires the `indexmap` feature.
pub fn find_cell_clusters<CellsIter>(cells: CellsIter) -> Result<Vec<Vec<H3Cell>>, Error>
where
    CellsIter: Iterator<Item = H3Cell>,
{
    Ok(find_cell_clusters_eq_value_impl(cells)?
        .into_values()
        .map(|(cluster, _)| cluster)
        .collect())
}

/// find clusters of neighboring cells where the same value is associated with the cells.
///
/// Cells are assumed to be unique, otherwise the behaviour is undefined.
///
/// Requires the `indexmap` feature.
pub fn find_cell_clusters_eq_value<CellValueIter, CV, Value>(
    cell_value_iter: CellValueIter,
) -> Result<Vec<(Vec<H3Cell>, Value)>, Error>
where
    CV: CellAndValue<Value>,
    CellValueIter: Iterator<Item = CV>,
    Value: PartialEq,
{
    Ok(find_cell_clusters_eq_value_impl(cell_value_iter)?
        .into_values()
        .collect())
}

pub trait CellAndValue<Value> {
    fn cell(&self) -> H3Cell;
    fn value(self) -> Value;
}

impl CellAndValue<()> for H3Cell {
    fn cell(&self) -> H3Cell {
        *self
    }

    fn value(self) {}
}

impl<Value> CellAndValue<Value> for (H3Cell, Value) {
    fn cell(&self) -> H3Cell {
        self.0
    }

    fn value(self) -> Value {
        self.1
    }
}

fn find_cell_clusters_eq_value_impl<CellValueIter, CV, Value>(
    cell_value_iter: CellValueIter,
) -> Result<HashMap<usize, (Vec<H3Cell>, Value)>, Error>
where
    CV: CellAndValue<Value>,
    CellValueIter: Iterator<Item = CV>,
    Value: PartialEq,
{
    let items: IndexMap<_, _, RandomState> =
        cell_value_iter.map(|cv| (cv.cell(), cv.value())).collect();
    let mut cluster_ids: Vec<usize> = (0..items.len()).collect();

    let mut mutated = true;
    let mut disk_builder = GridDiskBuilder::create(1, 1)?;
    while mutated {
        mutated = false;
        for (pos, (cell, value)) in items.iter().enumerate() {
            let mut least_cluster_id = cluster_ids[pos];
            for (neighbor_cell, _) in &mut disk_builder.build_grid_disk(cell)? {
                if let Some((neighbor_pos, _, neighbor_value)) = items.get_full(&neighbor_cell) {
                    if neighbor_value == value {
                        match cluster_ids[neighbor_pos].cmp(&least_cluster_id) {
                            Ordering::Less => {
                                least_cluster_id = cluster_ids[neighbor_pos];
                                cluster_ids[pos] = least_cluster_id;
                                mutated = true;
                            }
                            Ordering::Equal => {}
                            Ordering::Greater => {
                                cluster_ids[neighbor_pos] = least_cluster_id;
                                mutated = true;
                            }
                        }
                    }
                }
            }
        }
    }

    Ok(cluster_ids.into_iter().zip(items).fold(
        HashMap::default(),
        |mut acc, (group, (cell, value))| {
            match acc.entry(group) {
                Entry::Vacant(entry) => {
                    entry.insert((vec![cell], value));
                }
                Entry::Occupied(mut entry) => {
                    entry.get_mut().0.push(cell);
                }
            };
            acc
        },
    ))
}

#[cfg(test)]
mod tests {
    use crate::algorithm::find_cell_clusters;
    use crate::H3Cell;

    #[test]
    fn find_cell_clusters_simple() {
        let mut disk1: Vec<_> = H3Cell::from_coordinate((12.2, 14.5).into(), 6)
            .unwrap()
            .grid_disk(3)
            .unwrap()
            .iter()
            .collect();
        disk1.sort_unstable();
        let mut disk2: Vec<_> = H3Cell::from_coordinate((42.2, 45.5).into(), 6)
            .unwrap()
            .grid_disk(2)
            .unwrap()
            .iter()
            .collect();
        disk2.sort_unstable();

        let mut clusters =
            find_cell_clusters(disk1.iter().copied().chain(disk2.iter().copied())).unwrap();
        assert_eq!(clusters.len(), 2);
        let mut cluster1 = clusters.remove(0);
        cluster1.sort_unstable();
        let mut cluster2 = clusters.remove(0);
        cluster2.sort_unstable();
        assert!(cluster1 == disk1 || cluster1 == disk2);
        assert!(cluster2 == disk1 || cluster2 == disk2);
        assert_ne!(cluster1, cluster2);
    }
}