Function idwInterpolation

idwInterpolation<T extends Properties = Properties>(
    point: VectorPoint,
    refData: VectorPoint<T>[],
    getValue?: GetInterpolateValue<T>,
): number
Inverse Distance Weighting Interpolation
Description
Given a reference of data, interpolate a point using inverse distance weighting

Usage
```
import { idwInterpolation, PointIndexFast } from 'gis-tools-ts';
import type { VectorPoint } from 'gis-tools-ts';

// We have m-value data that we want to interpolate
interface TempData { temp: number; }

const pointIndex = new PointIndexFast<TempData>();
// add lots of points
pointIndex.insertLonLat(lon, lat, data);
// ....

// given a point we are interested in
const point: VectorPoint = { x: 20, y: -40 };
//  get a collection of points relative to the point
const data = await pointIndex.searchRadius(point.x, point.y, radius);

// interpolate
const interpolatedValue = idwInterpolation<TempData>(point, data, (p) => p.m.temp);
```
Type Parameters
- T extends Properties = Properties
Parameters
- point: VectorPoint
  point to interpolate
- refData: VectorPoint<T>[]
  reference data to interpolate from
- getValue: GetInterpolateValue<T> = defaultGetInterpolateCurrentValue
  function to get value from reference data. Can be the z value or a property in the m-values defaults to function that returns the z value or 0 if the z value is undefined
Returns number
- the interpolated value