get comparable homes given a zillow home ID

zcomps.R

getCompChain <- function(id, n = 100, asDT=FALSE, store = TRUE){
   fn_comp <- function(id){
      r     <- ZillowR::GetComps(zpid = id, count = 25, zws_id = zws)
      xll   <- XML::xmlToList(r$response)
      count <- ncol(xll["comparables", ][[1]])
      res <- lapply(1:count, function(iter){
         list(
            zpid    = xll['comparables', ][[1]]['zpid', ][[iter]],
            address = xll['comparables', ][[1]]['address', ][[iter]]
         )
      })
      return(res)
   }

   env_comp$cList <- NULL
   env_comp$total <- 0
   env_comp$ZID   <- NULL

   ## First Iteration
   ll             <- fn_comp(id)
   new_zids       <- sapply(1:length(ll), function(i) ll[[i]]$zpid)
   index          <- which(!new_zids %in% env_comp$ZID)
   env_comp$ZID   <- c(env_comp$ZID, new_zids[index])
   env_comp$cList <- c(env_comp$cList, ll[index])
   total          <- length(env_comp$ZID)

   ## Run remaining iterations
   tryCatch({

      iter  <- 1
      while(total < n){
         ll             <- fn_comp(env_comp$ZID[iter])
         new_zids       <- sapply(1:length(ll), function(i) ll[[i]]$zpid)
         index          <- which(!new_zids %in% env_comp$ZID)
         env_comp$ZID   <- c(env_comp$ZID, new_zids[index])
         env_comp$cList <- c(env_comp$cList, ll[index])

         total <- length(env_comp$ZID)
         iter  <- iter + 1

         # print update
         cat("\n")
         print(paste0("iteration: ", iter))
         print(paste0("total comps: ", total))
         cat("\n")
      }

   }, error = function(c){
      warning("parsing failed... returning completed data", call. = FALSE)
   })

   if(asDT)
      return(chainToDT(env_comp$cList))
   return(env_comp$cList)
}