# entropy

number, date, boolean or text data

## entropy(T.a : ‘a) 🡒 number, aggregator

Returns the Shannon Entropy of the group. The value is returned expressed in shannons. The entropy of an empty group is 0. Supported data types are number, text, date and boolean.

Example:

table T = with
[| as A, as B, as C, as D |]
[| 0, "a", date(2020, 1, 8) , true |]
[| 1, "a", date(2010, 9, 1) , true |]
[| 1, "b", date(2019, 12, 1), true |]

show summary "" a1b4 with
entropy(T.A)
entropy(T.B)
entropy(T.C)
entropy(T.D)


The entropy of an empty group is 0.

The entropy aggregator is typically intended to identify the columns of input files with little or no information.