From d001dc74ef8b51fb00c7aafc8ef48d6f69d538b0 Mon Sep 17 00:00:00 2001
From: Alexander Lalejini <amlalejini@gmail.com>
Date: Tue, 20 Oct 2020 15:43:47 -0400
Subject: [PATCH] Add standard error to stats.h

---
 source/tools/stats.h | 9 +++++++++
 tests/tools/stats.cc | 4 ++++
 2 files changed, 13 insertions(+)

diff --git a/source/tools/stats.h b/source/tools/stats.h
index b09a4be575..e865142fd5 100644
--- a/source/tools/stats.h
+++ b/source/tools/stats.h
@@ -111,6 +111,15 @@ namespace emp {
     return sqrt(Variance(elements));
   }
 
+  /// Calculate the standard error of the values in a container
+  /// If values are pointers, they will be automatically de-referenced
+  /// Values must be numeric.
+  template <typename C>
+  emp::sfinae_decoy<double, typename C::value_type>
+  StandardError(C & elements) {
+    return StandardDeviation(elements) / sqrt(elements.size());
+  }
+
   /// Count the number of unique elements in a container
   template <typename C>
   typename std::enable_if<!emp::is_ptr_type<typename C::value_type>::value, int>::type
diff --git a/tests/tools/stats.cc b/tests/tools/stats.cc
index d86d3a6fec..9ea1985565 100644
--- a/tests/tools/stats.cc
+++ b/tests/tools/stats.cc
@@ -33,6 +33,10 @@ TEST_CASE("Test stats", "[tools]") {
   REQUIRE(emp::StandardDeviation(vec2) == Approx(0.5).epsilon(0.001));
   REQUIRE(emp::StandardDeviation(deque1) == Approx(1.0488).epsilon(0.001));
 
+  REQUIRE(emp::StandardError(vec1) == Approx(0.3333).epsilon(0.001));
+  REQUIRE(emp::StandardError(vec2) == Approx(0.25).epsilon(0.001));
+  REQUIRE(emp::StandardError(deque1) == Approx(0.4281).epsilon(0.001));
+
   REQUIRE(emp::Sum(vec1) == 10);
   REQUIRE(emp::Sum(vec2) == 5);
   REQUIRE(emp::Sum(deque1) == 27);