simplify #sign

Author: gbuesing

examples/mnist.rb

@@ -94,7 +94,7 @@
 
 puts "\nTraining the network with #{train_size} data samples...\n\n"
 t = Time.now
-result = nn.train(x_train, y_train, log_every: 1, max_iterations: 100)
+result = nn.train(x_train, y_train, log_every: 1, max_iterations: 100, error_threshold:  0.005)
 
 puts "\nDone training the network: #{result[:iterations]} iterations, error #{result[:error].round(5)}, #{(Time.now - t).round(1)}s"
 

neural_net.rb

@@ -229,10 +229,12 @@ def mean_squared_error errors
     ZERO_TOLERANCE = Math.exp(-16)
 
     def sign x
-      if x < ZERO_TOLERANCE && x > -ZERO_TOLERANCE # if float very close to 0
-        0
+      if x > ZERO_TOLERANCE
+        1
+      elsif x < -ZERO_TOLERANCE
+        -1
       else
-        x <=> 0 # returns 1 if postitive, -1 if negative
+        0 # x is zero, or a float very close to zero
       end
     end