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use spatial index to speed up #34

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use spatial index to speed up #34

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44 changes: 38 additions & 6 deletions lib/methods/areal-weighting.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
const Turf = require('turf');
const Logger = require('../logger');
const isUndefined = require('lodash/isUndefined');
const rbush = require('rbush');

function main(source, target, options) {
target.features.forEach((d, i) => {
Expand All @@ -18,6 +19,7 @@ function arealWeighting(feature, source, options, attributeName) {
const intersectData = getIntersectingFeatures(source.features, feature);
const sourceFeatures = intersectData[0];
const intersects = intersectData[1];


intersects.forEach((d,i) => {
const Ps = parseFloat(sourceFeatures[i].properties[attributeName]);
Expand All @@ -32,18 +34,48 @@ function arealWeighting(feature, source, options, attributeName) {

function getIntersectingFeatures(sourceFeatures, targetFeature) {
let intersects = [];
let featureSimpl = targetFeature;
let sourceList = []; // source features that got intersected?

/* Create and fill the bushy tree */
var tree = rbush();
let items = [];

for (var i=0; i<sourceFeatures.length; i++) {
var bbox = Turf.extent(sourceFeatures[i]);
var item = {
minX: bbox[0],
minY: bbox[1],
maxX: bbox[2],
maxY: bbox[3],
index: i
};
items.push(item);
}

tree.load(items);

const sourceList = sourceFeatures.filter(f => {
let intersection = Turf.intersect(featureSimpl, f);
/* Quickly get the likely candidates that might intersect */
var bbox = Turf.extent(targetFeature);
var candidates = tree.search({
minX: bbox[0],
minY: bbox[1],
maxX: bbox[2],
maxY: bbox[3]
});

/* Check the candidates for actual intersection and do the rest */
for (var i=0; i<candidates.length; i++) {
var index = candidates[i].index;
var f = sourceFeatures[index];

let intersection = Turf.intersect(targetFeature, f);

if(!isUndefined(intersection)) {
intersection.properties = f.properties;
intersects.push(intersection);
sourceList.push(f);
}

return !isUndefined(intersection);
});
}

return [sourceList, intersects];
}
Expand Down