From 6211206b73cb2857d83bc5ce2e455c45990b4b45 Mon Sep 17 00:00:00 2001
From: Bert Chang <jrweizhang@gmail.com>
Date: Fri, 2 May 2014 21:10:55 +0800
Subject: [PATCH] Remove Metric interface, add RBFKernel.

---
 metrics/pairwise/pairwise.go   |  5 -----
 metrics/pairwise/rbf_kernel.go | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 5 deletions(-)
 create mode 100644 metrics/pairwise/rbf_kernel.go

diff --git a/metrics/pairwise/pairwise.go b/metrics/pairwise/pairwise.go
index a256038..a8df439 100644
--- a/metrics/pairwise/pairwise.go
+++ b/metrics/pairwise/pairwise.go
@@ -4,11 +4,6 @@ import (
 	mat "github.com/skelterjohn/go.matrix"
 )
 
-type Metric interface {
-	InnerProduct(vectorX *mat.DenseMatrix, vectorY *mat.DenseMatrix)
-	Distance(vectorX *mat.DenseMatrix, vectorY *mat.DenseMatrix)
-}
-
 func CheckDimMatch(vectorX *mat.DenseMatrix, vectorY *mat.DenseMatrix) bool {
 	if vectorX.Cols() != 1 ||
 		vectorY.Cols() != 1 ||
diff --git a/metrics/pairwise/rbf_kernel.go b/metrics/pairwise/rbf_kernel.go
new file mode 100644
index 0000000..22d132b
--- /dev/null
+++ b/metrics/pairwise/rbf_kernel.go
@@ -0,0 +1,33 @@
+package pairwise
+
+import (
+	"errors"
+	"math"
+
+	mat "github.com/skelterjohn/go.matrix"
+)
+
+type RBFKernel struct {
+	gamma float64
+}
+
+func NewRBFKernel(gamma float64) *RBFKernel {
+	return &RBFKernel{gamma: gamma}
+}
+
+func (self *RBFKernel) InnerProduct(vectorX *mat.DenseMatrix, vectorY *mat.DenseMatrix) (float64, error) {
+	if !CheckDimMatch(vectorX, vectorY) {
+		return 0, errors.New("Dimension mismatch")
+	}
+
+	euclidean := NewEuclidean()
+	distance, err := euclidean.Distance(vectorX, vectorY)
+
+	if err != nil {
+		return 0, err
+	}
+
+	result := math.Exp(self.gamma * math.Pow(distance, 2))
+
+	return result, nil
+}