New module `@turf/interpolate` (proposal) #832

stebogit · 2017-07-08T07:54:35Z

Implements #24

JSDocs

/**
 * Takes a set of points and estimates their 'property' values on a grid using the Inverse [Distance Weighting (IDW) method.](https://en.wikipedia.org/wiki/Inverse_distance_weighting).
 *
 * @name interpolate
 * @param {FeatureCollection<Point>} points with known value
 * @param {number} cellSize the distance across each grid point
 * @param {string} [gridType='square'] defines the output format based on a Grid Type (options: 'square' | 'point' | 'hex' | 'triangle')
 * @param {string} [property='elevation'] the property name in `points` from which z-values will be pulled
 * @param {string} [units=kilometers] used in calculating cellSize, can be degrees, radians, miles, or kilometers
 * @param {number} [weight=1] exponent regulating the distance-decay weighting
 * @returns {FeatureCollection<Point>} grid of points with 'property'
 */
module.exports = function (points, cellSize, property, units, weight) {

Example

var points = turf.random('points', 15, {
    bbox: [-75.9221, 39.11, -75.05, 39.987]
});
turf.featureEach(points, function(point) {
    point.properties.elevation = Math.random() * 50;
});
var cellSize = 5;
var grid = turf.interpolate(points, cellSize);

add zValue as 3rd coordinate if property is not defined.
add tests
add all other grid types to library.
might replace/integrate @turf/idw ?

@DenisCarriere following #829 I thought maybe it would make sense to implement this module with the IDW method. In fact I don't really know any other interpolation methods, but I'm open to suggestions.
However, this differs from @turf/idw only in outputting a pointGrid instead of a squareGrid. Does it make sense to have two modules here?
If not I would rather merge the two in a single turf-interpolate (I think is more clear to an average user like me, who ignored the meaning of IDW since this morning...) and add to the module an outputType parameter (default to one of the two).

@bakerac4 maybe you want to try this module out and see if it fits your needs.

added setColor function in test.js; removed unused dependences; modified test input;

stebogit · 2017-07-08T08:04:20Z

@DenisCarriere I don't know why the test pass in my computer, but not in Travis... 😞

DenisCarriere · 2017-07-08T22:26:15Z

I'll comment more later on this weekend, however for the Travis build fail, I'm guessing it's a decimal precision error, even using Node 6 vs. 7 you could have slight differences. Solution would be to use the @turf/truncate module on the result test/out.

Quick glance, this looks like an awesome module!

DenisCarriere · 2017-07-10T00:24:25Z

packages/turf-interpolate/test.js

+        const {property, cellSize, units, weight} = geojson.properties;
+
+        const grid = interpolate(geojson, cellSize, property, units, weight);
+        const result = colorize(grid, property);


Added @turf/truncate to results (reduce coordinates to 6 decimals).

Node 7 & 8 were passing, but Node 6 was failing (0.0000001 of a difference).

DenisCarriere · 2017-07-10T00:27:53Z

packages/turf-interpolate/index.d.ts

@@ -0,0 +1,10 @@
+/// <reference types="geojson" />
+
+import {Points} from '@turf/helpers';


Since @turf/helpers is not required in the main package.json, it might be better to include the Full GeoJSON typescript definition instead of importing it (in case the dependencies wouldn't include @turf/helpers).

type Point = GeoJSON.FeatureCollection<GeoJSON.Point>;

DenisCarriere · 2017-07-10T00:29:10Z

packages/turf-interpolate/index.d.ts

+/**
+ * http://turfjs.org/docs/#interpolate
+ */
+declare function interpolate(points: Points, cellSize: number, property?: number, units?: string, weight?:number): Points;


property?: number should be a string

Contradicts my previous comment, but units?: string could use Units instead of string.

import {Units} from '@turf/helpers'

ah! nice to know, I didn't noticed the types in @turf/helpers 👍

- truncate coordinate decimals - Update Typescript definition

DenisCarriere · 2017-07-10T00:52:38Z

packages/turf-interpolate/index.js

+    if (!points) throw new Error('points is required');
+    collectionOf(points, 'Point', 'input must contain Points');
+    if (!cellSize) throw new Error('cellSize is required');
+    if (cellSize === undefined || cellSize === null) throw new Error('cellWidth is required');


I'm going to assume this is a duplicate of cellSize.

CellSize cannot be 0, correct?

if (!cellSize) throw new Error('cellSize is required'); if (cellSize === undefined || cellSize === null) throw new Error('cellWidth is required');

DenisCarriere · 2017-07-10T01:19:14Z

Question: Should we add a round/precision property? That way the elevation properties can be rounded to a specific precision (starting to have a lot of options).

CC: @stebogit

- Add tests for throwing errors - Update Readme

DenisCarriere · 2017-07-10T01:54:36Z

packages/turf-interpolate/test/types.ts

@@ -0,0 +1,16 @@
+import * as linearc from '../index'


🤦‍♂️ Looks like this file came from the previous repo 🤣

I've been putting types.ts at the root directory that way we don't forget it.

One day... all modules will have types.ts to test for the Typescript definitions.

So far this one looks like this:

import * as interpolate from './'; import {point, featureCollection} from '@turf/helpers'; const cellSize = 1; const property = 'pressure'; const weight = 0.5; const units = 'miles'; const points = featureCollection([ point([1, 2]), point([12, 13]), point([23, 22]), ]); const grid = interpolate(points, cellSize, property, units, weight); grid.features[0].properties.pressure;

DenisCarriere

👍 Looks good to me!

DenisCarriere · 2017-07-10T02:43:05Z

@stebogit Should we add the 3rd coordinate as zValue if property is not defined? Like we did for (Modules to support z coordinate from geometry #628, Support z-coordinate as input for @turf/turf-tin #772).

DenisCarriere · 2017-07-10T03:00:45Z

might replace/integrate @turf/idw ?

Agreed, however the only difference with @turf/idw is the output is a FeatureCollection<Polygon>, if we can manage to have interpolate do both or simply integrate this library into idw but keep the output as polygons.

CC: @stebogit

stebogit · 2017-07-10T03:09:28Z

Should we add a round/precision property?

@DenisCarriere I don't see the number of decimals as an issue, the user can simply round it, if necessary, to the desired precision when using the interpolated value(s)

DenisCarriere · 2017-07-10T03:17:06Z

I don't see the number of decimals as an issue

👍 That works, yea it's not really an issue.

DenisCarriere · 2017-07-10T03:18:24Z

@stebogit Have a quick glance at it before we merge, I'm done with any edits.

DenisCarriere · 2017-07-10T03:21:46Z

If not I would rather merge the two in a single turf-interpolate (I think is more clear to an average user like me, who ignored the meaning of IDW since this morning...) and add to the module an outputType parameter (default to one of the two).

👍 Agreed, maybe once we bump up to a major release v5.0 we could do that.

I also prefer the term interpolate vs. IDW (even though this term is commonly used in GIS).

CC: @morganherlocker Thoughts?

stebogit · 2017-07-10T04:01:02Z

Agreed, however the only difference with @turf/idw is the output is a FeatureCollection<Polygon>, if we can manage to have interpolate do both or simply integrate this library into idw but keep the output as polygons.

@DenisCarriere yes, having this module doing both is really easy (I'll implement that).

I also prefer the term interpolate vs. IDW (even though this term is commonly used in GIS).

👍 we could add an outputType = 'squares'|'points' parameter ~~, defaulting to 'polygon'~~.
~~This module should also be faster than the current implementation of idw.~~

When I implemented this I was wondering if @morganherlocker had actually a different idea/algorithm of interpolation in mind when suggesting this module

stebogit · 2017-07-10T04:10:18Z

BTW anybody knows if there is a more appropriate default value for weight?

stebogit · 2017-07-10T08:36:29Z

@DenisCarriere I added the outputType parameter.
I thought to define it as required, so the user has to consciously choose the output; also if we wanted to extend it to hexGrids or triangleGrid we could easily.

DenisCarriere · 2017-07-10T20:59:27Z

👍 I like the option of defining the different outputType, we could call it gridType and the avaible options should be exactly the same singular name as the Grid module (point instead of points).

Defining a default param should be fine, we can use square as the default since it's the default for idw and if we replace that module with interpolate then it wouldn't be such a drastic change.

/**
 * @param {string} [gridType='square'] defines the output format based on a Grid Type (options: 'square' | 'point')

DenisCarriere · 2017-07-10T22:09:12Z

Last edits before we merge:

Add all other grid types to library.

updated docs, yarn.lock, bench, index.d.ts; added tests;

stebogit · 2017-07-11T15:33:23Z

@DenisCarriere good to merge I believe.
Nice and colorful module, particularly handy in combo with isobands and isolines! 😃

DenisCarriere · 2017-07-11T17:47:02Z

Love it!! Super excited to release this module in the next minor release!

stebogit added 6 commits April 12, 2017 01:21

added module folder

9bbfdad

replaced loops with featureEach;

971d1df

added setColor function in test.js; removed unused dependences; modified test input;

Merge branch 'master' into turf-interpolate

3acd8cb

reimplemented module with IDW

a11aebc

add yarn.lock file

5755018

updated package.json

d76b61f

stebogit added the new-module label Jul 8, 2017

stebogit self-assigned this Jul 8, 2017

stebogit requested a review from DenisCarriere July 8, 2017 07:54

stebogit changed the title ~~New module @turf/interpolate~~ New module @turf/interpolate (proposal) Jul 8, 2017

DenisCarriere reviewed Jul 10, 2017

View reviewed changes

DenisCarriere added 2 commits July 9, 2017 20:47

Ignore @turf/helpers since it can be used in Typescript definitions

2db7a8f

Fix tests

bb89170

- truncate coordinate decimals - Update Typescript definition

DenisCarriere reviewed Jul 10, 2017

View reviewed changes

DenisCarriere added 2 commits July 9, 2017 21:20

Fix tests - Round elevation property

2659aea

- Add tests for throwing errors - Update Readme

Upgrade typescript dev dependency

2cd7100

DenisCarriere reviewed Jul 10, 2017

View reviewed changes

Remove un-used types.ts file

0195c9f

DenisCarriere approved these changes Jul 10, 2017

View reviewed changes

Add zValue from 3rd coordinate

35ab0d3

DenisCarriere added 2 commits July 9, 2017 23:02

Update example with turf.interpolate

749a575

Update docs related to 3rd coordinate zValue

86fbc4c

added outputType parameter

1abe3dc

adjusted test color scale: darker is higher value

66de2d0

DenisCarriere added 2 commits July 10, 2017 17:11

Change outputType to gridType

5556ee3

Create switch statement to easily extend GridTypes

9b8031b

DenisCarriere added this to the 4.6.0 milestone Jul 10, 2017

added hex and triangle grid type;

8883eb2

updated docs, yarn.lock, bench, index.d.ts; added tests;

DenisCarriere merged commit 926836a into master Jul 11, 2017

DenisCarriere deleted the turf-interpolate branch July 11, 2017 17:48

stebogit mentioned this pull request Jul 13, 2017

New module @turf/interpolate #24

Closed

DenisCarriere mentioned this pull request Aug 2, 2017

New minor release! Turf 4.6.0 🎉 #884

Closed

stebogit mentioned this pull request Aug 3, 2017

Deprecate @turf/idw ? #887

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New module `@turf/interpolate` (proposal) #832

New module `@turf/interpolate` (proposal) #832

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		@@ -0,0 +1,10 @@
		/// <reference types="geojson" />

		import {Points} from '@turf/helpers';

New module @turf/interpolate (proposal) #832

New module @turf/interpolate (proposal) #832

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Example

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