From b047b8f546273b0dff5ef585ec00398b3450c9de Mon Sep 17 00:00:00 2001
From: Isabelle Viktoria Maciohsek <maciv@hotmail.gr>
Date: Sat, 14 Mar 2020 11:33:48 +0200
Subject: [PATCH] Add frequencies

---
 frequencies.md | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 frequencies.md

diff --git a/frequencies.md b/frequencies.md
new file mode 100644
index 000000000..f260e7353
--- /dev/null
+++ b/frequencies.md
@@ -0,0 +1,22 @@
+---
+title: frequencies
+tags: list,intermediate
+---
+
+Returns a dictionary with the unique values of a list as keys and their frequencies as the values.
+
+Use a `for` loop to populate a dictionary, `f`, with the unique values in `lst` as keys, adding to existing keys every time the same value is encountered.
+
+```py
+from functools import reduce
+
+def frequencies(lst):
+  f = {}
+  for x in lst:
+    f[x] = f[x] + 1 if x in f else 1
+  return f
+```
+
+```py
+frequencies(['a', 'b', 'a', 'c', 'a', 'a', 'b']) # { 'a': 4, 'b': 2, 'c': 1 }
+```