automatically set goal limits using GIS data

[jeffreyhanson]

@josephrbennett had the idea of automatically setting goal limits (for beginner mode) based on GIS data (e.g. by overlaying a feature's distribution data with a protected area layer). This could be really useful to inlcude in the GIS plugin tool that JC's working on - what do you think @JCLaurence and @ricschuster?

[DanWismer]

@ricschuster could we use the calculate_targets function here to set goals for the user that reflect the proportion of features:

calculate_targets <- function(x, minimum_range_size = 1000,
                                  proportion_at_minimum_range_size = 1,
                                  maximum_range_size = 250000,
                                  proportion_at_maximum_range_size = 0.1,
                                  cap_range_size = 10000000,
                                  cap_target_amount = 1000000) {
      # initialization
      out <- rep(NA_real_, length(x))
      pos <- which(is.finite(x))
      # set targets below threshold
      out[pos] <- stats::approx(
        x = log10(c(minimum_range_size, maximum_range_size)),
        y = c(proportion_at_minimum_range_size,
              proportion_at_maximum_range_size),
        xout = log10(x[pos]), method = "linear", rule = 2)$y
      # set caps
      cap_pos <- which(x > cap_range_size)
      if (length(cap_pos) > 0) {
        out[cap_pos] <- cap_target_amount / x[cap_pos]
      }
      # return values
      return(out)
    }

    goal <- calculate_targets(x)
  } else {
    goal <- ""
  }