R/latlon_is.valid.R

In ejanalysis/proxistat: Create a Proximity Score in Each Census Unit, Based on Distances to Specified Points (as in EPA's EJScreen tool, for example)

#' Validate latitudes and longitudes
#' @description Check each latitude and longitude value to see if they are 
#'   NA or outside expected numeric ranges 
#'   (based on approx ranges of lat lon seen among block internal points dataset)
#'   lat must be between 17.5 and 71.5, and 
#'   lon must be ( between -180 and -64) OR (between 172 and 180) 
#' @param lon numeric vector of longitudes in decimal degrees, same length
#' @param lat vector of latitudes in decimal degrees
#' @quiet optional logical, if TRUE, show list of bad values in console
#' @return logical vector, one element per lat lon pair (location)
#' @seealso latlon_df_clean() latlon_infer() latlon_is.valid() latlon_as.numeric()
#' @examples  \dontrun{
#'  table(latlon_is.valid(lat =  frs$lat, lon =  frs$lon))
#'  table(latlon_is.valid(lat =  blockpoints$lat, lon =  blockpoints$lon))
#'   }
#' @export
#'
latlon_is.valid <- function(lon, lat, quiet=TRUE) {
  
  # TRUE only if both lat and lon seem valid:
  if( any(is.na(lat)) || any(is.na(lon)) ) {
    bad <- is.na(lat) | is.na(lon)
  } else {
    bad <- rep(FALSE, length(lat))
  }
  bad <- bad | lat < 17.5 | lat > 71.5 | lon < -180 | (lon > -64 & lon < 172) | lon > 180
  
  if (any(bad)) {
    warning('Some lat or lon values seem invalid - NA or number outside expected range')
  }
  if (!quiet & any(bad)) {
    cat('\nSeemingly invalid lat lon points:\n\n ')
    print(data.table(lat = lat[bad], lon = lon[bad]))
    cat('\n\n') 
  }
  
  return(!bad)
  
  
  #     valid ranges determined like this:  
  #   > range(blockpoints$lat)
  # [1] 17.88513 71.39840
  # > # lat must be between 17.5 and 71.5
  # 
  # > min(blockpoints$lon[blockpoints$lon > -65])
  # [1] 172.5912 # and must be < 180 (one is at 179.6212)
  # > max(blockpoints$lon[blockpoints$lon < 0])
  # [1] -65.20799 # and must be > -180 (min seen is -179.1084)
  # > # lon must be ( between -180 and -65) OR (between 172 and 180) -- but actually US VI might reach almost -64 longitude
  
  # BUT NOTE FRS SEEMS TO HAVE PROBLEMATIC LAT LON VALUES
  # > range(frs$lat)
  # [1] -43.78711  88.07278
  # > range(frs$lon)
  # [1] -179.3000  179.2599
  
  # > table(latlon_is.valid(frs$lon, frs$lat))
  # 
  # FALSE    TRUE 
  # 1384 3454658
  # 
}