R/nearestsiteFUN.R

In gmiskell/sensor_toolkit: Functions for Managing Sensor Networks

#' Identify Nearest Site. 
#'
#' This function gives the proxy type of nearest site data.
#' @param obs This is the column being examined.
#' @param group This is the grouping variable.
#' @param lat Latitude column.
#' @param lon Longitude column.
#' @export
#' @examples
#' nearestsiteFUN()

nearestsiteFUN <- function(x, obs, group, lat, lon){

	library(tidyverse)

	# define variables
	x <- as.data.frame(x)
	x$obs <- x[[obs]]; x$group <- x[[group]]; x$lat <- x[[lat]]; x$lon <- x[[lon]];

	# find closest sites
	y <- x %>%
		dplyr::select(group, lat, lon) %>%
		unique()

	d <- as.matrix(dist(cbind(y$lon, y$lat)))
	d <- data.frame(d)
	colnames(d) <- c(as.character(d$group), 'group')
	min.d <- apply(d, 1, function(x) order(x, decreasing = F)[2])
	newdata <- cbind(y, y[min.d,], apply(d, 1, function(x) sort(x, 	decreasing=F)[2]))
	colnames(newdata) <- c(colnames(y), 'n.group', 'n.lat', 'n.lon', 'distance')

	# combine the data with appropriate proxy
	df3 <- full_join(x, newdata, by = 'group')
	x$nearest.proxy <- x$obs
	x$obs <- NULL

	finaldata <- left_join(df3, x, by = c('date', 'n.group' = 'group'))
	finaldata <- finaldata %>%
		dplyr::select(date, group, obs, nearest.proxy)
}