Isoline from example returning MultiLineString with no coordinates

[bakerac4]

Following the example found at http://turfjs.org/docs/#isolines after downloading the minified turf.js file and including it in my project ends up giving me 10 features that each have 1 geometry object inside, with type MultiLineString that has an empty array of coordinates.

Here is a GIST of the GeoJSON I am getting back
https://gist.github.com/bakerac4/89656a65e7388b290d223facdaf5dc75

The code I am using seems to be a copy and paste from the docs.

var points = turf.random('point', 100, {
  bbox: [0, 30, 20, 50]
});
for (var i = 0; i < points.features.length; i++) {
  points.features[i].properties.temperature = Math.random() * 10;
}
var breaks = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
var isolines = turf.isolines(points, breaks, 'temperature');

[DenisCarriere]

Huh... interesting.

Also getting the same result:

//= isoloines.features[0]
{ type: 'Feature',
  properties: { temperature: 1 },
  geometry: { type: 'MultiLineString', coordinates: [] } }

Thoughts? @stebogit

[stebogit]

@bakerac4 turf-isolines (like turf-isobands) expects a pointGrid as input, which will be internally converter into a matrix (Array<Array<number>>) of zProperty values to be able to calculate the isolines. With just random points there is no matrix (that's why a @turf/interpolate module has been desirable for long time).
If you have though a matrix and you want to convert it into a pointGrid you could use matrix-to-grid.

I'm surprised (and sorry) the documentation have not been correctly updated when the module was re-implemented, I'll commit the appropriate correction.

[stebogit]

Done. I did also fix a small bug in isobands and made sure also its example was working.
@DenisCarriere how can I update also the API website?

[bakerac4]

Thank you @stebogit for clearing that up. That leaves me a bit confused (and Im sure its just me misunderstanding something). Does pointGrid create a grid of points that are always evenly spaced out?

Im trying to create a isoline heatmap like this but I am being given a list of objects (with lat, lng and temp). From what Im gathering, since turf/interpolate doesn't actually exist yet Im out of luck?

Thanks again for your help !

[stebogit]

Does pointGrid create a grid of points that are always evenly spaced out?

Yes @bakerac4, this is an example of pointGrid output

I'm trying to create a isoline heatmap like this

You might want to take a look at @turf/isobands then, it's probably what you need as it created the contour polygons instead of just the isolines.

I'm out of luck?

Look at @turf/idw, it might give you some hints on how to generate a pointGrid.

[DenisCarriere]

@bakerac4 interpolation operations with TurfJS can be significantly improved, like @stebogit was mentioning, you might have a better result using one of these TurfJS libraries:

• @turf/idw
• @turf/isobands

[Ir001]

Im using isobands for creating contour. If i using Math.random() for zProperty value its work

,but if i use real data isoband returning MultiPolygon with empty coordinates.