def variance(source: Observable) -> Observable:
"""
Returns the statistical variance of the numerical emissions.
The sequence must be finite.
"""
squared_values = (
source.to_list().flat_map(lambda l: Observable.from_(l).average(
).flat_map(lambda avg: Observable.from_(l).map(lambda i: i - avg)
)).map(lambda i: i * i).publish().auto_connect(2))
return Observable.zip(squared_values.sum(), squared_values.count(),
lambda sum, ct: sum / (ct - 1))
def mode(source: Observable[Any]) -> Observable[Any]:
"""
Returns the most frequently emitted value (or "values" if they have the same number of occurrences).
The sequence must be finite.
"""
return (source.group_by(lambda v: v).flat_map(
lambda grp: grp.count().map(lambda ct: (grp.key, ct))).to_sorted_list(
lambda t: t[1], reverse=True).flat_map(lambda l: Observable.from_(
l).take_while(lambda t: t[1] == l[0][1])).map(lambda t: t[0]))
