Fixed anomalous test

lib/carl.js

@@ -1,13 +1,11 @@
 var gauss = require('gauss');
 var gaussian = require('gaussian');
 
-var epsilon = 0.05;
-
 var Carl = module.exports = function(mean, variance, epsilon) {
   this.mean = mean || 0;
   this.variance = variance || 1;
   this.distribution = gaussian(this.mean, this.variance);
-  this.epsilon = epsilon;
+  this.epsilon = epsilon || 0.05;
 };
 
 Carl.prototype.train = function(data, callback) {
@@ -32,8 +30,11 @@ Carl.prototype.cdf = function(x) {
 };
 
 Carl.prototype.isAnomalous = function(x) {
-  var p = 1 - this.cdf(Math.abs(x));
-  return p < epsilon/2;
+  var p = this.cdf(x);
+  if(p > 0.5) {
+    p = 1 - p;
+  }
+  return p < this.epsilon/2;
 };
 
 Carl.prototype.isValid = function(x) {

test/carl.test.js

@@ -12,6 +12,7 @@ describe('Carl', function() {
     var carl = new Carl();
     carl.mean.should.equal(0);
     carl.variance.should.equal(1);
+    carl.epsilon.should.equal(0.05);
     round(carl.pdf(1)).should.eql(0.242);
   });
 
@@ -38,6 +39,12 @@ describe('Carl', function() {
     round(carl.cdf(-2)).should.eql(0.023);
   });
 
+  it('should use mean, variance and epsilon from constructor parameters to detect anomaly', function() {
+    var carl = new Carl(0.161388, 0.007538945, 0.1);
+    carl.isAnomalous(0.1).should.be.false;
+    carl.isAnomalous(0.01).should.be.true;
+  });
+
   it('should determine significance with epsilon .05', function() {
     var carl = new Carl();
     carl.isAnomalous(0).should.be.false;