## formatNum

updated 2016-12-18

Prettifies numbers, especially for plotting

`round_mean`

calculates mean and rounds to a number of digits. Returns a double.`round_std`

calculates standard deviation and rounds to a number of digits. Returns a double.`round_exact`

rounds value to a number of digits, preserving trailing zeros. Returns a string.`percent`

converts a ratio to a percentage with a number of digits and a percent sign, e.g. 0.125 –> “12.5%”