R/buildDeltaProb2.R

In bogdanoancea/deduplication: R package for computing the duplicity probility for each mobile device.

#' @title Computes the probability distribution for Delta X and Delta Y.
#'
#' @description Computes the probability distribution for Delta X and Delta Y 
#' where Delta X / Delta Y are the differences between the centroids of the tiles 
#' on OX / OY. For a detailed explanation of what Delta X and Delta Y
#' mean please refer to \href{https://webgate.ec.europa.eu/fpfis/mwikis/essnetbigdata/images/f/fb/WPI_Deliverable_I3_A_proposed_production_framework_with_mobile_network_data_2020_05_31_draft.pdf}{WPI
#'    Deliverable 3}.
#' The posterior location probability for each tile nd each device comes from 
#' \pkg{destim}.
#'
#' @param centroids The centroids of all tiles in the grid.
#'
#' @param postLocProbDevice1 The location probability of the first device, 
#' at a certain time instant, for each tile in the grid.
#'
#' @param postLocProbDevice2 The location probability of the first device, 
#' at a certain time instant, for each tile in the grid.
#'
#' @return a list with two data.table objects, the first is the probability 
#' distribution for Delta X and the second for
#'   Delta Y. The list items are named DeltaX and DeltaY.
#'
#' @keywords internal
#' @import data.table
#' @export
buildDeltaProb2 <-function(centroids, postLocProbDevice1, postLocProbDevice2) {
  xp1<-cbind(centroids[,.(x,y)], postLocProbDevice1)
  xp2<-cbind(centroids[,.(x,y)], postLocProbDevice2)
  
  colnames(xp1)<-c('x1', 'y1', 'p1')
  colnames(xp2)<-c('x2', 'y2', 'p2')
  
  xp1<-xp1[p1!=0][,]
  xp2<-xp2[p2!=0][,]
  deltaX <- CJ.table(xp1[,.(x1,p1)],xp2[,.(x2,p2)])
  deltaX <- deltaX[, delta:=x1-x2]
  deltaX <- deltaX[, p:=p1*p2]
  deltaX <- deltaX[, .(delta, p)]
  deltaX<-deltaX[, lapply(.SD,sum), by=.(delta)]
  
  deltaY <- CJ.table(xp1[,.(y1,p1)],xp2[,.(y2,p2)])
  deltaY <- deltaY[, delta:=y1-y2]
  deltaY <- deltaY[, p:=p1*p2]
  deltaY <- deltaY[, .(delta, p)]
  deltaY<-deltaY[, lapply(.SD,sum), by=.(delta)]
  
  return(list(deltaX=deltaX, deltaY=deltaY))
}



CJ.table <- function(X,Y) {
  setkey(X[,c(k=1,.SD)],k)[Y[,c(k=1,.SD)],allow.cartesian=TRUE][,k:=NULL]
}