TypeScript helpers.convertLength函數代碼示例

/**
 * Returns the minimum distance between a {@link Point} and a {@link LineString}, being the distance from a line the
 * minimum distance between the point and any segment of the `LineString`.
 *
 * @name pointToLineDistance
 * @param {Feature<Point>|Array<number>} pt Feature or Geometry
 * @param {Feature<LineString>} line GeoJSON Feature or Geometry
 * @param {Object} [options={}] Optional parameters
 * @param {string} [options.units="kilometers"] can be anything supported by turf/convertLength
 * (ex: degrees, radians, miles, or kilometers)
 * @param {string} [options.method="geodesic"] wether to calculate the distance based on geodesic (spheroid) or
 * planar (flat) method. Valid options are 'geodesic' or 'planar'.
 * @returns {number} distance between point and line
 * @example
 * var pt = turf.point([0, 0]);
 * var line = turf.lineString([[1, 1],[-1, 1]]);
 *
 * var distance = turf.pointToLineDistance(pt, line, {units: 'miles'});
 * //=69.11854715938406
 */
function pointToLineDistance(pt: Coord, line: Feature<LineString> | LineString, options: {
    units?: Units,
    method?: "geodesic" | "planar",
} = {}): number {
    // Optional parameters
    if (!options.method) { options.method = "geodesic"; }
    if (!options.units) { options.units = "kilometers"; }

    // validation
    if (!pt) { throw new Error("pt is required"); }
    if (Array.isArray(pt)) { pt = point(pt);
    } else if (pt.type === "Point") { pt = feature(pt);
    } else { featureOf(pt, "Point", "point"); }

    if (!line) { throw new Error("line is required"); }
    if (Array.isArray(line)) { line = lineString(line);
    } else if (line.type === "LineString") { line = feature(line);
    } else { featureOf(line, "LineString", "line"); }

    let distance = Infinity;
    const p = pt.geometry.coordinates;
    segmentEach(line, (segment) => {
        const a = segment!.geometry.coordinates[0];
        const b = segment!.geometry.coordinates[1];
        const d = distanceToSegment(p, a, b, options);
        if (d < distance) { distance = d; }
    });
    return convertLength(distance, "degrees", options.units);
}

/**
 * Calculates the distance along a rhumb line between two {@link Point|points} in degrees, radians,
 * miles, or kilometers.
 *
 * @name rhumbDistance
 * @param {Coord} from origin point
 * @param {Coord} to destination point
 * @param {Object} [options] Optional parameters
 * @param {string} [options.units="kilometers"] can be degrees, radians, miles, or kilometers
 * @returns {number} distance between the two points
 * @example
 * var from = turf.point([-75.343, 39.984]);
 * var to = turf.point([-75.534, 39.123]);
 * var options = {units: 'miles'};
 *
 * var distance = turf.rhumbDistance(from, to, options);
 *
 * //addToMap
 * var addToMap = [from, to];
 * from.properties.distance = distance;
 * to.properties.distance = distance;
 */
function rhumbDistance(from: Coord, to: Coord, options: {
    units?: Units,
} = {}): number {
    const origin = getCoord(from);
    const destination = getCoord(to);

    // compensate the crossing of the 180th meridian (https://macwright.org/2016/09/26/the-180th-meridian.html)
    // solution from https://github.com/mapbox/mapbox-gl-js/issues/3250#issuecomment-294887678
    destination[0] += (destination[0] - origin[0] > 180) ? -360 : (origin[0] - destination[0] > 180) ? 360 : 0;
    const distanceInMeters = calculateRhumbDistance(origin, destination);
    const distance = convertLength(distanceInMeters, "meters", options.units);
    return distance;
}

/**
 * Returns the destination {@link Point} having travelled the given distance along a Rhumb line from the
 * origin Point with the (varant) given bearing.
 *
 * @name rhumbDestination
 * @param {Coord} origin starting point
 * @param {number} distance distance from the starting point
 * @param {number} bearing varant bearing angle ranging from -180 to 180 degrees from north
 * @param {Object} [options={}] Optional parameters
 * @param {string} [options.units='kilometers'] can be degrees, radians, miles, or kilometers
 * @param {Object} [options.properties={}] translate properties to destination point
 * @returns {Feature<Point>} Destination point.
 * @example
 * var pt = turf.point([-75.343, 39.984], {"marker-color": "F00"});
 * var distance = 50;
 * var bearing = 90;
 * var options = {units: 'miles'};
 *
 * var destination = turf.rhumbDestination(pt, distance, bearing, options);
 *
 * //addToMap
 * var addToMap = [pt, destination]
 * destination.properties['marker-color'] = '#00F';
 */
function rhumbDestination<P = Properties>(origin: Coord, distance: number, bearing: number, options: {
    units?: Units,
    properties?: P,
} = {}): Feature<Point, P> {
    
    const wasNegativeDistance = distance < 0;
    let distanceInMeters = convertLength(Math.abs(distance), options.units, "meters");
    if (wasNegativeDistance) distanceInMeters = -Math.abs(distanceInMeters);
    const coords = getCoord(origin);
    const destination = calculateRhumbDestination(coords, distanceInMeters, bearing);

    // compensate the crossing of the 180th meridian (https://macwright.org/2016/09/26/the-180th-meridian.html)
    // solution from https://github.com/mapbox/mapbox-gl-js/issues/3250#issuecomment-294887678
    destination[0] += (destination[0] - coords[0] > 180) ? -360 : (coords[0] - destination[0] > 180) ? 360 : 0;
    return point(destination, options.properties);
}

/**
 * Takes a set of {@link Point|points} and partition them into clusters according to {@link DBSCAN's|https://en.wikipedia.org/wiki/DBSCAN} data clustering algorithm.
 *
 * @name clustersDbscan
 * @param {FeatureCollection<Point>} points to be clustered
 * @param {number} maxDistance Maximum Distance between any point of the cluster to generate the clusters (kilometers only)
 * @param {Object} [options={}] Optional parameters
 * @param {string} [options.units="kilometers"] in which `maxDistance` is expressed, can be degrees, radians, miles, or kilometers
 * @param {boolean} [options.mutate=false] Allows GeoJSON input to be mutated
 * @param {number} [options.minPoints=3] Minimum number of points to generate a single cluster,
 * points which do not meet this requirement will be classified as an 'edge' or 'noise'.
 * @returns {FeatureCollection<Point>} Clustered Points with an additional two properties associated to each Feature:
 * - {number} cluster - the associated clusterId
 * - {string} dbscan - type of point it has been classified as ('core'|'edge'|'noise')
 * @example
 * // create random points with random z-values in their properties
 * var points = turf.randomPoint(100, {bbox: [0, 30, 20, 50]});
 * var maxDistance = 100;
 * var clustered = turf.clustersDbscan(points, maxDistance);
 *
 * //addToMap
 * var addToMap = [clustered];
 */
function clustersDbscan(points: FeatureCollection<Point>, maxDistance: number, options: {
    units?: Units,
    minPoints?: number,
    mutate?: boolean
} = {}): FeatureCollection<Point, DbscanProps> {
    // Input validation being handled by Typescript
    // collectionOf(points, 'Point', 'points must consist of a FeatureCollection of only Points');
    // if (maxDistance === null || maxDistance === undefined) throw new Error('maxDistance is required');
    // if (!(Math.sign(maxDistance) > 0)) throw new Error('maxDistance is invalid');
    // if (!(minPoints === undefined || minPoints === null || Math.sign(minPoints) > 0)) throw new Error('options.minPoints is invalid');

    // Clone points to prevent any mutations
    if (options.mutate !== true) points = clone(points);

    // Defaults
    options.minPoints = options.minPoints || 3;

    // create clustered ids
    var dbscan = new clustering.DBSCAN();
    var clusteredIds = dbscan.run(coordAll(points), convertLength(maxDistance, options.units), options.minPoints, distance);

    // Tag points to Clusters ID
    var clusterId = -1;
    clusteredIds.forEach(function (clusterIds) {
        clusterId++;
        // assign cluster ids to input points
        clusterIds.forEach(function (idx) {
            var clusterPoint = points.features[idx];
            if (!clusterPoint.properties) clusterPoint.properties = {};
            clusterPoint.properties.cluster = clusterId;
            clusterPoint.properties.dbscan = 'core';
        });
    });

    // handle noise points, if any
    // edges points are tagged by DBSCAN as both 'noise' and 'cluster' as they can "reach" less than 'minPoints' number of points
    dbscan.noise.forEach(function (noiseId) {
        var noisePoint = points.features[noiseId];
        if (!noisePoint.properties) noisePoint.properties = {};
        if (noisePoint.properties.cluster) noisePoint.properties.dbscan = 'edge';
        else noisePoint.properties.dbscan = 'noise';
    });

    return points;
}