std

df.std() // std of values per every numeric column
df.std { age and weight } // std of all values in `age` and `weight`
df.stdFor { age and weight } // std of values per `age` and `weight` separately, skips NA
df.stdOf { (weight ?: 0) / age } // std of expression evaluated for every row

df.std()
df.age.std()
df.groupBy { city }.std()
df.pivot { city }.std()
df.pivot { city }.groupBy { name.lastName }.std()