implement the kernel part

Author: maasencioh

.gitignore

@@ -25,3 +25,6 @@ build/Release
 # Dependency directory
 # https://www.npmjs.org/doc/misc/npm-faq.html#should-i-check-my-node_modules-folder-into-git
 node_modules
+
+# generated by webstorm, I think
+.idea

.idea/workspace.xml

@@ -1 +1,2 @@
-exports.svm = require('./svm');
+exports.svm = require('./svm');
+exports.kernel = require('./kernel');

src/index.js

@@ -0,0 +1,52 @@
+'use strict';
+
+module.exports = function kernel(x1,x2,func,par) {
+    /**
+     * Kernel function to return the dot product for different spaces
+     *
+     * @param x1: first set of input vectors
+     * @param x2: second set of input vectors
+     * @param func: the kind of transformation
+     * @param par: parameter used in the polynomial and the radial function
+     * @return ans: calculus of the dot product using the function
+     * */
+
+    func = (typeof func === 'undefined') ? 'lineal' : func;
+    par = (typeof par === 'undefined') ? 2 : par;
+
+    // The dot product between the p1 and p2 vectors
+    var dot = function (p1, p2) {
+        if (p1.length !== p2.length) {
+            console.log("Don't have the same length");
+            return undefined;
+        }
+        var l = p1.length;
+        var prod = 0;
+
+        for (var i = 0; i < l; i++) {
+            prod += p1[i] * p2[i];
+        }
+
+        return prod;
+    };
+
+    var p = dot(x1,x2);
+    if (func === 'lineal'){
+        return p;
+    }
+    else if(func === 'polynomial') {
+        return Math.pow((p + 1), par);
+    }
+    else if(func === 'radial') {
+        var l = x1.length;
+        var rest = new Array(l);
+        for (var i = 0; i < l; i++) {
+            rest[i] = x1[i] - x2[i];
+        }
+        var norm = dot(rest, rest);
+        return Math.exp((norm)/(-2*par*par));
+    }
+    else {
+        return undefined;
+    }
+};

src/kernel.js

@@ -1,3 +1,6 @@
+'use strict';
+
+var kernel = require("./kernel");
 module.exports = function svm() {
     return 0;
 };

src/svm.js

@@ -0,0 +1,28 @@
+'use strict';
+
+var kernel = require('../src/kernel.js');
+
+var v1 = [0, 1, 4, 6, 2];
+var v2 = [0, 2, 5, 6, 7];
+
+describe('kernel test', function () {
+
+    it('no change product', function () {
+        kernel(v1,v2).should.equal(72);
+        kernel(v1,v2,"lineal").should.equal(72);
+    });
+
+    it('polynomial product', function () {
+        kernel(v1,v2,"polynomial").should.equal(5329);
+        kernel(v1,v2,"polynomial",2).should.equal(5329);
+        kernel(v1,v2,"polynomial",3).should.equal(389017);
+    });
+
+    it('radial product', function () {
+        kernel(v1,v2,"radial").should.be.approximately(0.03421811831,0.0001);
+        kernel(v1,v2,"radial",2).should.be.approximately(0.03421811831,0.0001);
+        kernel(v1,v2,"radial",3).should.be.approximately(0.22313016014,0.0001);
+    });
+
+
+});