adding activation funcs

alg/interface.go

@@ -1,6 +0,0 @@
-package alg
-
-type Alg interface {
-	New()
-	Train()
-}

nn/activation.go

@@ -1,19 +1,41 @@
 package nn
 
-var ActivationMap = map[string]func(){
+import "math"
+
+var ActivationMap = map[string]func(float64) float64{
 	"sigmoid": Sigmoid,
 	"tanh":    Tanh,
 	"relu":    Relu,
 }
 
-func Sigmoid() {}
+func Sigmoid(x float64) float64 {
+	return 1.0 / (1.0 + math.Exp(-x))
+}
 
-func SigmoidPrime() {}
+func SigmoidPrime(x float64) float64 {
+	s := Sigmoid(x)
+	return s / (1.0 - s)
+}
 
-func Tanh() {}
+func Tanh(x float64) float64 {
+	return math.Tanh(x)
+}
 
-func TanhPrime() {}
+func TanhPrime(x float64) float64 {
+	return math.Pow((1.0 / math.Cosh(x)), 2)
+}
 
-func Relu() {}
+func Relu(x float64) float64 {
+	if x > 0 {
+		return x
+	}
+	return 0
+}
 
-func ReluPrime() {}
+func ReluPrime(x float64) float64 {
+	// maybe want to look into edge case if x == 0
+	if x > 0 {
+		return 1
+	}
+	return 0
+}