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lukas-hlukas-h
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add initial line_slice_along implementation (#190)
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‎Progress.md‎

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@@ -77,7 +77,7 @@ Dart. This is an on going project and functions are being added once needed. If
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- [x] [lineOverlap](https://github.com/dartclub/turf_dart/blob/main/lib/src/line_overlap.dart)
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- [x] [lineSegment](https://github.com/dartclub/turf_dart/blob/main/lib/src/line_segment.dart)
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- [x] [lineSlice](https://github.com/dartclub/turf_dart/blob/main/lib/src/line_slice.dart)
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- [ ] lineSliceAlong
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- [x] [lineSliceAlong](https://github.com/dartclub/turf_dart/blob/main/lib/src/line_slice_along.dart)
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- [ ] lineSplit
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- [ ] mask
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- [x] [nearestPointOnLine](https://github.com/dartclub/turf_dart/blob/main/lib/src/nearest_point_on_line.dart)

‎lib/line_slice_along.dart‎

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library turf_line_slice_along;
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export 'package:geotypes/geotypes.dart';
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export "src/line_slice_along.dart";

‎lib/src/line_slice_along.dart‎

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import 'package:turf/bearing.dart';
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import 'package:turf/destination.dart';
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import 'package:turf/distance.dart';
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import 'package:turf/helpers.dart';
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/// Takes a [line], at a start distance [startDist] and a stop distance [stopDist]
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/// and returns a subsection of the line in-between those distances.
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///
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/// If [startDist] and [stopDist] resolve to the same point on [line], null is returned
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/// as the resolved line would only contain one point which isn't supported by LineString.
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///
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/// This can be useful for extracting only the part of a route between distances on the route.
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LineString lineSliceAlongRaw(
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LineString line,
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double startDist,
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double stopDist, [
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Unit unit = Unit.kilometers,
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]) {
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List<Position> coords = line.coordinates;
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var slice = <Position>[];
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var origCoordsLength = coords.length;
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double travelled = 0;
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double? overshot;
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double direction = 0;
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Position? interpolated;
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for (var i = 0; i < coords.length; i++) {
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if (startDist >= travelled && i == coords.length - 1) {
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break;
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} else if (travelled > startDist && slice.isEmpty) {
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overshot = startDist - travelled;
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if (overshot == 0) {
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slice.add(coords[i]);
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return LineString(coordinates: slice);
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}
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direction = bearingRaw(coords[i], coords[i - 1]) - 180;
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interpolated = destinationRaw(coords[i], overshot, direction, unit);
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slice.add(interpolated);
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}
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if (travelled >= stopDist) {
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overshot = stopDist - travelled;
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if (overshot == 0) {
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slice.add(coords[i]);
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return LineString(coordinates: slice);
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}
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direction = bearingRaw(coords[i], coords[i - 1]) - 180;
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interpolated = destinationRaw(coords[i], overshot, direction, unit);
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slice.add(interpolated);
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return LineString(coordinates: slice);
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}
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if (travelled >= startDist) {
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slice.add(coords[i]);
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}
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if (i == coords.length - 1) {
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return LineString(coordinates: slice);
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}
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travelled += distanceRaw(coords[i], coords[i + 1], unit);
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}
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if (travelled < startDist && coords.length == origCoordsLength) {
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throw Exception("Start position is beyond line");
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}
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final last = coords[coords.length - 1];
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return LineString(coordinates: [last, last]);
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}
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/// Takes a [line], at a start distance [startDist] and a stop distance [stopDist]
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/// and returns a subsection of the line in-between those distances.
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///
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/// If [startDist] and [stopDist] resolve to the same point on [line], null is returned
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/// as the resolved line would only contain one point which isn't supported by LineString.
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///
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/// This can be useful for extracting only the part of a route between distances on the route.
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Feature<LineString> lineSliceAlong(
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Feature<LineString> line,
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double startDist,
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double stopDist, [
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Unit unit = Unit.kilometers,
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]) {
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return Feature<LineString>(
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geometry: lineSliceAlongRaw(line.geometry!, startDist, stopDist, unit),
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properties: line.properties,
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);
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}

‎lib/turf.dart‎

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@@ -22,6 +22,7 @@ export 'line_intersect.dart';
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export 'line_overlap.dart';
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export 'line_segment.dart';
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export 'line_slice.dart';
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export 'line_slice_along.dart';
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export 'line_to_polygon.dart';
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export 'meta.dart';
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export 'midpoint.dart';

‎test/components/line_slice_along_test.dart‎

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import 'package:test/test.dart';
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import 'package:turf/turf.dart';
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import '../context/load_test_cases.dart';
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void main() {
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loadGeoJson('./test/examples/line_slice_along/fixtures/line1.geojson',
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(path, geoJson) {
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final line1 = Feature<LineString>(
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geometry: (geoJson as Feature).geometry as LineString,
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);
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test('turf-line-slice-along -- line1', () {
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const start = 500.0;
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const stop = 750.0;
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const options = Unit.miles;
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final startPoint = along(line1, start, options);
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final endPoint = along(line1, stop, options);
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final sliced = lineSliceAlong(line1, start, stop, options);
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expect(sliced, isA<Feature<LineString>>());
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expect(sliced.type, GeoJSONObjectType.feature);
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expect(sliced.geometry?.type, GeoJSONObjectType.lineString);
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expect(sliced.geometry?.coordinates[0],
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equals(startPoint.geometry!.coordinates));
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expect(
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sliced.geometry?.coordinates[sliced.geometry!.coordinates.length - 1],
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equals(endPoint.geometry!.coordinates),
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);
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});
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test('turf-line-slice-along -- line1 overshoot', () {
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const start = 500.0;
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const stop = 1500.0;
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const options = Unit.miles;
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final startPoint = along(line1, start, options);
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final endPoint = along(line1, stop, options);
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final sliced = lineSliceAlong(line1, start, stop, options);
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expect(sliced, isA<Feature<LineString>>());
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expect(sliced.type, GeoJSONObjectType.feature);
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expect(sliced.geometry?.type, GeoJSONObjectType.lineString);
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expect(sliced.geometry?.coordinates[0],
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equals(startPoint.geometry!.coordinates));
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expect(
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sliced.geometry?.coordinates[sliced.geometry!.coordinates.length - 1],
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equals(endPoint.geometry!.coordinates),
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);
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});
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test('turf-line-slice-along -- start longer than line length', () {
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const start = 500000.0;
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const stop = 800000.0;
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const options = Unit.miles;
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expect(
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() => lineSliceAlong(line1, start, stop, options),
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throwsA(isA<Exception>().having(
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(e) => e.toString(),
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'message',
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contains('Start position is beyond line'),
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)),
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);
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});
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test('turf-line-slice-along -- start equal to line length', () {
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const options = Unit.miles;
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final start = length(line1, options);
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final stop = start + 100;
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final startPoint = along(line1, start, options);
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final endPoint = along(line1, stop, options);
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final sliced =
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lineSliceAlong(line1, start.toDouble(), stop.toDouble(), options);
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expect(sliced, isA<Feature<LineString>>());
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expect(sliced.type, GeoJSONObjectType.feature);
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expect(sliced.geometry?.type, GeoJSONObjectType.lineString);
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expect(sliced.geometry?.coordinates[0],
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equals(startPoint.geometry!.coordinates));
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expect(
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sliced.geometry?.coordinates[sliced.geometry!.coordinates.length - 1],
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endPoint.geometry!.coordinates,
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);
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});
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});
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loadGeoJson('./test/examples/line_slice_along/fixtures/route1.geojson',
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(path, geoJson) {
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final route1 = Feature<LineString>(
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geometry: (geoJson as Feature).geometry as LineString,
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);
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test('turf-line-slice-along -- route1', () {
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const start = 500.0;
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const stop = 750.0;
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const options = Unit.miles;
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final startPoint = along(route1, start, options);
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final endPoint = along(route1, stop, options);
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final sliced = lineSliceAlong(route1, start, stop, options);
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expect(sliced, isA<Feature<LineString>>());
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expect(sliced.type, GeoJSONObjectType.feature);
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expect(sliced.geometry?.type, GeoJSONObjectType.lineString);
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expect(sliced.geometry?.coordinates[0],
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equals(startPoint.geometry!.coordinates));
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expect(
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sliced.geometry?.coordinates[sliced.geometry!.coordinates.length - 1],
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equals(endPoint.geometry!.coordinates),
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);
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});
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});
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loadGeoJson('./test/examples/line_slice_along/fixtures/route2.geojson',
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(path, geoJson) {
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final route2 = Feature<LineString>(
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geometry: (geoJson as Feature).geometry as LineString,
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);
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test('turf-line-slice-along -- route2', () {
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const start = 25.0;
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const stop = 50.0;
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const options = Unit.miles;
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final startPoint = along(route2, start, options);
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final endPoint = along(route2, stop, options);
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final sliced = lineSliceAlong(route2, start, stop, options);
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expect(sliced, isA<Feature<LineString>>());
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expect(sliced.type, GeoJSONObjectType.feature);
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expect(sliced.geometry?.type, GeoJSONObjectType.lineString);
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expect(sliced.geometry?.coordinates[0],
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equals(startPoint.geometry!.coordinates));
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expect(
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sliced.geometry?.coordinates[sliced.geometry!.coordinates.length - 1],
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equals(endPoint.geometry!.coordinates),
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);
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});
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});
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}

‎test/examples/line_slice_along/fixtures/line1.geojson‎

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{
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"type": "Feature",
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"properties": {},
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"geometry": {
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"type": "LineString",
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"coordinates": [
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[113.99414062499999, 22.350075806124867],
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[116.76269531249999, 23.241346102386135],
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[117.7734375, 24.367113562651276],
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[118.828125, 25.20494115356912],
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[119.794921875, 26.78484736105119],
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[120.80566406250001, 28.110748760633534],
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[121.59667968749999, 29.49698759653577],
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[121.59667968749999, 31.12819929911196],
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[120.84960937499999, 32.84267363195431],
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[119.83886718750001, 34.125447565116126],
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[118.69628906249999, 35.31736632923788],
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[121.4208984375, 36.80928470205937],
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[122.82714843749999, 37.37015718405753]
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]
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}
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}

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