nearestbyday: Merge two point datasets by day.

In allanjust/aodlur: Tools For Land Use Regression With AOD

Description

Merge point datasets by day to the closest of K nearest neighbors (with an optional distance constraint).

Usage

nearestbyday(jointo.pts, joinfrom.pts, jointo, joinfrom, jointovarname,
  joinfromvarname, joinprefix = "closest", valuefield = "avewsp",
  knearest = 5, maxdistance = NA, nearestmean = FALSE, verbose = FALSE)

Arguments

jointo.pts	points matrix output from makepointsmatrix
joinfrom.pts	points matrix output from makepointsmatrix
jointo	data.table target
joinfrom	data.table data source
jointovarname	column name for unique field for points in jointo
joinfromvarname	column name for unique field for points in joinfrom
joinprefix	string to use as name for new variables
valuefield	column name with field to be merged in
knearest	number of nearest neighbors to check for non-missing data
maxdistance	(optional) constraint on distance, in the units of the points matrix
nearestmean	(optional) also compute mean of knearest values within maxdistance?
verbose	print output of the intermediate data.table size and fields

Value

A data.table, akin to a semi_join on nearest neighbor and day.

Examples

jointo <- data.table(x = 1:5, y = 1:5, siteidx = 1:5,
                    day = as.Date("2004-04-01"))
joinfrom <- data.table(x = rep(1:5 + 0.1, times = 5),
                      y = rep(1:5, each = 5), 
                      siteidy = letters[1:25], # currently this needs to be character
                      value = 100 + 1:25,
                      day = as.Date("2004-04-01"))
                      
jointo.pt <- makepointsmatrix(datatable = jointo, 
                             xvar = "x", yvar = "y", idvar = "siteidx") 
joinfrom.pt <- makepointsmatrix(datatable = joinfrom, 
                               xvar = "x", yvar = "y", idvar = "siteidy") 
joinout <- nearestbyday(jointo.pts = jointo.pt, joinfrom.pts = joinfrom.pt, 
                       jointo = jointo, joinfrom = joinfrom, 
                       jointovarname = "siteidx", joinfromvarname = "siteidy", 
                       joinprefix = "nearest", valuefield = "value", 
                       knearest = 3, maxdistance = 2, 
                       nearestmean = TRUE, verbose = TRUE)
joinout                        

allanjust/aodlur documentation built on May 10, 2019, 9:22 a.m.