[R] Calculate Distances

after.R

#' Vectorize
bld_ids     <- as.character(df_localdb_dt$bld_id)
target_long <- df_localdb_dt$long
target_lat  <- df_localdb_dt$lat

#' Calculate distances 
dt_dist <- foreach(chunk = isplitVector(1:nrow(df_localdb_dt), chunks=getDoParWorkers()), .packages = c("foreach", "geodist"),.combine = c, .verbose = T) %dopar% { 
	dt_tot <- foreach(x = chunk, .inorder = F, .packages = c("geodist")) %do% { 
		# Reduce the range to search 
		map_to_rn <- df_rndata_dt[lat < target_lat[x] + threshold & lat > target_lat[x] - threshold & 
								long < target_long[x] + threshold & long > target_long[x] - threshold ,] 
		map_to_PS <- df_PSdata_dt[lat < target_lat[x] + threshold & lat > target_lat[x] - threshold & 
								long < target_long[x] + threshold & long > target_long[x] - threshold ,] 
		distRN <- as.vector(geodist(cbind(long=target_long[x], lat=target_lat[x]) , map_to_rn[, c("long", "lat")])) 
	
    	hm_content <- new.env() 
		hm_content$bld_id  <- bld_ids[x] 
		hm_content$rn_id  <- map_to_rn$rn_id[which.min(distRN)] 
		hm_content$distrn  <- distRN[which.min(distRN)] 
		hm_content$pos_cd  <- map_to_PS$pos_cd 
		hm_content$distPOS <- as.vector(geodist(cbind(long=target_long[x], lat=target_lat[x]) , map_to_PS[, c("long", "lat")])) 
	  	return(hm_content) 
	} 
	gc()
    return(dt_tot) 
} 


#' Combind 
df_comb <- foreach(chunk = isplitVector(dt_dist, chunks=getDoParWorkers()), .packages = c("foreach", "data.table"), .verbose = T) %dopar% { 
	dt_list <- foreach(content = chunk, .packages = c("data.table")) %do% { 
		dt_rn <- data.table( 
					bld_id = rep(content$bld_id, length(content$rn_id)), 
					type = rep("RN", length(content$rn_id)), 
					code = content$rn_id, 
					distance = ceiling(content$distrn), 
					stringsAsFactors = F ) 
		dt_pos <- data.table( 
					bld_id = rep(content$bld_id, length(content$pos_cd)), 
					type = rep("PS", length(content$pos_cd)), 
					code = content$pos_cd, 
					distance = ceiling(content$distPOS), 
					stringsAsFactors = F ) 
		return(rbindlist(l = list(dt_rn, dt_pos), use.names = F)) 
	} 
	gc()
    return(rbindlist(l = dt_list, use.names = F)) 
} 
result <- rbindlist(l=df_comb, use.names = F) 

before.R

dt_dist <- foreach(chunk = isplitVector(df_localdb_dt_bld$bld_id, chunks=getDoParWorkers()), .packages = c("foreach", "geodist", "dplyr"),.combine = rbind, .verbose = T) %dopar% {  
	dt_tot < - foreach(x = chunk, .combine = rbind, .inorder = F, .packages = c("dplyr", "geodist")) %do% {
        # Reduce the range to search 
    	map_from_localdb <- df_localdb_dt_bld %>% filter( bld_id == x ) %>% dplyr::select( long, lat )
    	map_to_rn <- df_rndata_dt %>% filter(
        	lat <=  map_from_localdb$lat + threshold & lat >= map_from_localdb$lat - threshold &  
          	long <=  map_from_localdb$long + threshold & long >= map_from_localdb$long - threshold)
        map_to_PS <- df_PSdata_dt %>% filter(
            lat <=  map_from_localdb$lat + threshold & lat >= map_from_localdb$lat - threshold &  
            long <=  map_from_localdb$long + threshold & long >= map_from_localdb$long - threshold
   
    	rn_nrow  <- nrow(map_to_rn)
    	pos_nrow <- nrow(map_to_PS)
    	maxCnt   <- min(rn_nrow, pos_nrow)    
            
        if(maxCnt==0) return(NULL)    

    	distRN <- geodist(map_from_localdb, map_to_rn[, c("long", "lat")])
	    distPS <- geodist(map_from_localdb, map_to_PS[, c("long", "lat")])    
	    idxRN  <- order(distRN) %>% head(maxCnt)
	    idxPS  <- order(distPS) %>% head(maxCnt)    
	    dt  <- data.frame(bld_id=rep(x, maxCnt),
                          RN_ID=map_to_rn$eqip_id[idxRN],
                          RN_LOC_BLD_ID=map_to_rn$bld_id[idxRN],
                          distRN= distRN[idxRN],
                          POS_CD=map_to_PS$pos_cd[idxPS],
                          distPOS= distPS[idxPS],
                          stringsAsFactors = FALSE)
        return(dt)
  }
  return(dt_tot)
}