The function uses a randomized approach to test the significance of the Clark-Evans R statistic:
the observed R value is set against the distribution of R values computed across B iterations
(199 by default) in which a set of random points (with a sample size equal to the number of
points of the input feature) is drawn and the statistic recomputed.
The function produces a histogram of the randomized R values, with a black dot indicating the
observed value and a hollow dot representing the average of the randomized R values. P-values
(computed following Baddeley et al., "Spatial Point Patterns. Methodology and Applications with
R", CRC Press 2016, p. 387), are reported at the bottom of the same chart. Two reference lines
represent the two tails of the randomized distribution (left tail, indicating a significant
clustered pattern; right tail, indicating a significant dispersed pattern).