From 601bfc9411f70f84a7ba94132844990d349c4d23 Mon Sep 17 00:00:00 2001
From: ergz <emnlrodriguez@gmail.com>
Date: Sat, 3 Sep 2022 01:51:37 -0700
Subject: [PATCH] working through examples of conditional probs

---
 R/ch2.R | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/R/ch2.R b/R/ch2.R
index 7694ce4..dd8a069 100644
--- a/R/ch2.R
+++ b/R/ch2.R
@@ -25,3 +25,22 @@ fake_news|>
     tally() |> 
     mutate(prop = n / sum(n))
 
+# usage of "!" in fake vs real articles
+fake_news |> 
+    group_by(type, title_has_excl) |> 
+    summarise(
+        total_usage_of_excl = n()
+    ) |> 
+    ungroup() |>
+    group_by(type) |> 
+    summarise(
+        prop_excl_within_type = total_usage_of_excl / sum(total_usage_of_excl), 
+        title_has_excl
+    ) |> 
+    filter(type == "fake")
+
+# P(A ^ B) = P(A|B)*P(B)
+# P(B) = .4
+# P(A|B) = .2667
+# => P(A|B)*P(B)
+.4 * .2667