Add categorize LISA function for labeling lisa clusters

[JosiahParry]

This was previously implemented in sfweight and would be a good utility to make avaialble to people

function(x, x_lag, scale = TRUE) {

  cats <- character(length(x))

  if (scale) {
    x <- scale(x)
    x_lag <- scale(x_lag)

    cats[x > 0 & x_lag > 0] <- "HH"
    cats[x > 0 & x_lag < 0] <- "HL"
    cats[x < 0 & x_lag < 0] <- "LL"
    cats[x < 0 & x_lag > 0] <- "LH"

  }

  cats[x > mean(x) & x_lag > mean(x_lag)] <- "HH"
  cats[x > mean(x) & x_lag < mean(x_lag)] <- "HL"
  cats[x < mean(x) & x_lag < mean(x_lag)] <- "LL"
  cats[x < mean(x) & x_lag > mean(x_lag)] <- "LH"
  cats[cats == ""] <- NA
  cats
}