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utils.js
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utils.js
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const bbox = require('@turf/bbox').default;
const concaveman = require('concaveman');
const destination = require('@turf/destination').default;
const helpers = require('@turf/helpers');
const pointGrid = require('@turf/point-grid').default;
const makeGrid = (startPoint, options) => {
const point = helpers.point(startPoint);
const spokes = helpers.featureCollection([
destination(point, options.radius, 180, options.unit),
destination(point, options.radius, 0, options.unit),
destination(point, options.radius, 90, options.unit),
destination(point, options.radius, -90, options.unit)
]);
const bboxGrid = bbox(spokes);
const grid = pointGrid(bboxGrid, options.cellSize, { units: options.units });
return grid.features.map(feature => feature.geometry.coordinates);
};
const groupByInterval = (destinations, intervals, travelTime) =>
intervals.reduce((pointsByInterval, interval) => {
const intervalInSeconds = interval * 60;
pointsByInterval[interval] = destinations.reduce((acc, point, index) => {
if (travelTime[index] !== null && travelTime[index] <= intervalInSeconds) {
acc.push(point.location);
}
return acc;
}, []);
return pointsByInterval;
}, {});
const makePolygon = (points, interval, options) => {
const concave = concaveman(points, options.concavity, options.lengthThreshold);
return helpers.polygon([concave], { time: parseFloat(interval) });
};
const makePolygons = (pointsByInterval, options) =>
Object.keys(pointsByInterval).reduce((acc, interval) => {
const points = pointsByInterval[interval];
if (points.length >= 3) {
acc.push(makePolygon(points, interval, options));
}
return acc;
}, []);
module.exports = { makeGrid, groupByInterval, makePolygons };