GeneralFunction

Geo: NEAREST (LT, LN, TLT, TLN)

Returns the row number of the nearest point in a lookup table of latitudes and longitudes

Purpose

Use this function to:

Identify the nearest lookup location to a set of coordinates
Find nearest geographical place
Create a continuous integer key that can be used to link to a lookup table

Return Value

Property	Value
FieldType	Integer
FieldSize	Continuous
DataType	Continuous
DataSize	Integer

Example Return Value: 1 to N, where N is the number of rows in the lookup table

Nearest_data

Parameters

Parameter	JSON	Description
Table	“targetTable”: “MyTableName”	The target table on which the new field will be created
Filter	“dataset”: {DataSet_JSON}	Optional. If a filter is applied, records not in the filter DataSet will be returned as null.
Function	"function":"geo"	Geo
Geo Function	"p1": "NEAREST(LT,LN,TLT,TLN)"	NEAREST(LT,LN,TLT,TLN)
LT	“p2”: "lat"	Required. The field on the targetTable containing the latitude value. Supports: DataType: Discrete/Continuous Field Type: Double Fixed Value: #nn.nnnnnnn
LN	“p3”: "lon"	Required. The field on the targetTable containing the longitude value Supports: DataType: Discrete/Continuous Field Type: Double Fixed Value: #nn.nnnnnnn
TLT	“p4”: "worldcities.lat"	Required. The fully qualified column on the lookup table that contains latitude. Supports: DataType: Discrete/Continuous Field Type: Double Fixed Value: #nn.nnnnnnn
TLN	“p5”:"worldcities.lng"	Required. The fully qualified column on the lookup table that contains longitude. Supports: DataType: Discrete/Continuous Field Type: Double Fixed Value: #nn.nnnnnnn

JSON Sample

{
  "method": "BuildBakedField",
  "project": "Model1",
  "targetTable": "BikePoints",
  "overwrite": true,
  "name": "Nearest",
  "function": "geo",
  "p1": "NEAREST(LT,LN,TLT,TLN)",
  "p2": "lat",
  "p3": "lon",
  "p4": "worldcities.lat",
  "p5": "worldcities.lng"
}

Usage Notes

NEAREST returns an continuous integer key into the lookup table. Use this key to create a key to the lookup table, and then copy up specific data-points as required.

Example targetTable:

targetTable

Example Lookup Table:

LookupTable

Example

Example	Details
Description	Obtain lookup of world city that is nearest to BikePoint
Input	Table: = [BikePoint] Function:= Geo Filter: = [No Filter] Geo Function: = NEAREST(LT, LN, TLT, TLN) LT:= lat LN:= lon TLT:= worldcities.lat TLN:= worldcities.lon Name: =Nearest
Sample

NEAREST(LT, LN, TLT, TLN)