node-idw

inverse distance weighted interpolation for nodejs in C++
-----

```
var options = {
nth: ?,
same: ?,
neighbor: ?,
loLim: ?,
upLim: ?
}
``
--------

nth:

Nth power to calculate the weight from distance :

weight = distance^nth

Default value is 1.

--------

same:

Threshold of same point check :

A given point will be considered as the same point of the grid point,

if the distance between them is lower than this threshold.

The value of the grid point will be set to the value of the given point,

And the interpolation process for this grid point will stop immediately.

Default value is 2 * DBL_MIN.

--------


neighbor:

Threshold of neighborhood check :

A given point will NOT be considered a neighbor of the grid point,

if the distance between them is larger than this threshold.

Only neighbor points have effect on the grid point,

which means the given point will be skiped if it is not a neighbor.

Default value is DBL_MAX.

--------


loLim:

Lower limit :

If the value of a given point is lower than this limit,

it will be skiped, unless it is the same point of the grid point.

Default value is -DBL_MAX.

--------

upLim:

Upper limit. same.

Default value is DBL_MAX.

--------
``
const idw = require('idw')
...
points = [
{value: 10, longitude: 11, latitude: 12},
{value: 1, longitude: 2, latitude: 3},
{value: 7, longitude: 8, latitude: 9},
{value: 4, longitude: 5, latitude: 6},
...
]
x = Array.from({length: width}, (v,k)=> x(k))
y = Array.from({length: height}, (v,k)=> y(k))

var interpolated = idw.sync(points, x, y, [options])

callback = (interpolated) => {
...
}

idw.async(points, x, y, [options], callback)
``

or


``
const idw = require('idw')
value = [10,1,7,4,...]
x = [11,2,8,5,...]
y=[12,3,9,6,...]
X = Array.from({length: width}, (v,k)=> X(k))
Y = Array.from({length: height}, (v,k)=> Y(k))

var interpolated = idw.sync(value, x, y, X, Y, [options])

callback = (interpolated) => {
...
}

idw.async(value, x, y, X, Y, [options], callback)
```