Fixed check for zero probability value in JensenShannon and updated test.

stat.go

@@ -402,9 +402,11 @@ func JensenShannon(p, q []float64) float64 {
 	for i, v := range p {
 		qi := q[i]
 		m := 0.5 * (v + qi)
-		if m != 0 {
+		if v != 0 {
 			// add kl from p to m
 			js += 0.5 * v * (math.Log(v) - math.Log(m))
+		}
+		if qi != 0 {
 			// add kl from q to m
 			js += 0.5 * qi * (math.Log(qi) - math.Log(m))
 		}

stat_test.go

@@ -357,6 +357,10 @@ func TestJensenShannon(t *testing.T) {
 		js1 := 0.5*KullbackLeibler(p, m) + 0.5*KullbackLeibler(q, m)
 		js2 := JensenShannon(p, q)
 
+		if math.IsNaN(js2) {
+			t.Errorf("In case %v, JS distance is NaN", i)
+		}
+
 		if math.Abs(js1-js2) > 1e-14 {
 			t.Errorf("JS mismatch case %v. Expected %v, found %v.", i, js1, js2)
 		}