Data update

Task/Entropy/DuckDB/entropy.duckdb

@@ -0,0 +1,16 @@
+# h should be a DuckDB histogram and n should be map_values(h).list_sum()
+create or replace function h2e(h, n) as (
+  - map_values(h).list_transform( x -> x * log2(x/n)).list_sum() / n
+);
+
+# str is normally a string but if not, will be cast to one
+create or replace function shannon_entropy(str) as (
+  with cte as (
+    from unnest( string_split(str::VARCHAR,'')) _(s)
+  ),
+  n as (select count(*) as n from cte),
+  h as (select histogram(s) as h from cte)
+  select h2e(h,n) from h, n
+);
+
+select shannon_entropy(1223334444);