The data itself neatly splits into areas where there are several hundred or thousand of observations and areas where there are relatively few (in most cases less than 100 and often less than 50).
Mae’r data yn rhannu’n daclus i feysydd lle mae cannoedd neu filoedd o arsylwadau a meysydd lle nad oes llawer o gwbl (llai na 100 yn y rhan fwyaf o achosion a llai na 50).