I am looking for an equation to calculate appropriate intervals to designate values as very low, low, medium, high, very high for dynamic data.
for example if my dataset ranges from 0 to 100 very low= <=20, low=21-40, medium=41-60, high=61-80, very high= >81
However, if the range is small there should be fewer ranges. For example, if the range is 20 then there should be a low and high interval designation only.
the intervals need to be logical intervals so they can be used for a graphical display. logical intervals would include intervals of 5, 10, 25, 50, 100 etc depending on the dataset. Is there an equation that can determine appropriate intervals for each unique dataset?