Improve search_radius speed

[StefanMusch]

The search_radius function is incredibly slow because it's created in a loop instead of being vectorized. A quick and dirty speed up could be:

search_radius_fast <- function(lat, lng, radius = 1) {
  
  # Filter out invalid coordinates
  zip_data <- zip_code_db %>%
    filter(!is.na(lat) & !is.na(lng))
  
  # Vectorized distance calculation (meters → miles)
  zip_data$distance <-
    raster::pointDistance(
      c(lng, lat),
      zip_data[, c("lng", "lat")],
      lonlat = TRUE
    ) * 0.000621371
  
  # Filter and arrange by distance
  
  result <- zip_data %>% dplyr::filter(.data$distance <= radius) %>% 
    dplyr::select(.data$zipcode, .data$distance) %>% dplyr::as_tibble() %>% 
    dplyr::arrange(.data$distance)
  
  if (nrow(result) == 0) {
    warning(paste("No ZIP codes found for coordinates", 
                  paste0(lat, ",", lng), "with radius", radius, "mi"))
  }
  return(result)
  }

This already speeds up the function by a margin of about 40.