From c79093821df2ed3017cd9c011229e877c4d574d9 Mon Sep 17 00:00:00 2001
From: nicholasbalasus <91984611+nicholasbalasus@users.noreply.github.com>
Date: Mon, 27 Dec 2021 05:25:51 -0500
Subject: [PATCH] Add atan support for missings (#43523)

Allowing atan to deal with two missing arguments
---
 base/math.jl    |  3 +++
 test/missing.jl | 13 +++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/base/math.jl b/base/math.jl
index 9a5e5377cf613..704557adc5f2e 100644
--- a/base/math.jl
+++ b/base/math.jl
@@ -1318,6 +1318,9 @@ for f in (:sin, :cos, :tan, :asin, :atan, :acos,
     end
     @eval $(f)(::Missing) = missing
 end
+atan(::Missing, ::Missing) = missing
+atan(::Number, ::Missing) = missing
+atan(::Missing, ::Number) = missing
 
 exp2(x::AbstractFloat) = 2^x
 exp10(x::AbstractFloat) = 10^x
diff --git a/test/missing.jl b/test/missing.jl
index 0be8cb8ec9be4..c20dc21f188d3 100644
--- a/test/missing.jl
+++ b/test/missing.jl
@@ -109,6 +109,19 @@ end
     end
 end
 
+@testset "two-argument functions" begin
+    two_argument_functions = [atan]
+
+    # All two-argument functions return missing when operating on two missing's
+    # All two-argument functions return missing when operating on a scalar and an missing
+    # All two-argument functions return missing when operating on an missing and a scalar
+    for f in two_argument_functions
+        @test ismissing(f(missing, missing))
+        @test ismissing(f(1, missing))
+        @test ismissing(f(missing, 1))
+    end
+end
+
 @testset "bit operators" begin
     bit_operators = [&, |, ⊻]