From 6536a791edd7a4f7a51b281bcebffe92fc5d2241 Mon Sep 17 00:00:00 2001
From: Krishna Vedala <7001608+kvedala@users.noreply.github.com>
Date: Sun, 31 May 2020 07:48:53 -0400
Subject: [PATCH] define activation function

---
 machine_learning/adaline_learning.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/machine_learning/adaline_learning.cpp b/machine_learning/adaline_learning.cpp
index 750341378..18c79ecbb 100644
--- a/machine_learning/adaline_learning.cpp
+++ b/machine_learning/adaline_learning.cpp
@@ -85,7 +85,7 @@ class adaline {
         // for (int i = 0; i < x.size(); i++) y += x[i] * weights[i];
         y = std::inner_product(x.begin(), x.end(), weights.begin(), y);
 
-        return y >= 0 ? 1 : -1;  // quantizer: apply ADALINE threshold function
+        return activation(y);  // quantizer: apply ADALINE threshold function
     }
 
     /**
@@ -150,6 +150,8 @@ class adaline {
                       << std::endl;
     }
 
+    friend int activation(double x) { return x > 0 ? 1 : -1; }
+
  private:
     /**
      * convenient function to check if input feature vector size matches the