[Stats] add tTest statistics to have p-value from 2 vectors

ummisco.gaml.extensions.maths/META-INF/MANIFEST.MF

@@ -11,6 +11,7 @@ Export-Package: org.apache.commons.math3.ml.clustering,
  org.apache.commons.math3.random,
  org.apache.commons.math3.stat.descriptive,
  org.apache.commons.math3.stat.descriptive.moment,
+ org.apache.commons.math3.stat.inference,
  org.apache.commons.math3.stat.regression,
  org.apache.commons.math3.util,
  ummisco.gaml.extensions.maths.ode.statements

ummisco.gaml.extensions.stats/src/ummisco/gaml/extensions/stats/Stats.java

@@ -25,6 +25,7 @@
 import org.apache.commons.math3.random.MersenneTwister;
 import org.apache.commons.math3.stat.descriptive.moment.Kurtosis;
 import org.apache.commons.math3.stat.descriptive.moment.Skewness;
+import org.apache.commons.math3.stat.inference.TTest;
 
 import com.google.common.collect.Ordering;
 
@@ -1080,6 +1081,30 @@ public static IList<IList> KMeansPlusplusApache(final IScope scope, final IList
 			return results.items();
 		}
 	}
+
+	@operator (
+			value = "tTest",
+			can_be_const = false,
+			category = { IOperatorCategory.STATISTICAL },
+			concept = { IConcept.STATISTIC })
+	@doc (
+			value = "Returns the observed significance level, or p-value, associated with a two-sample, "
+					+ "two-tailed t-test comparing the means of the two input lists."
+					+ "The number returned is the smallest significance level at which one can reject the null hypothesis",
+			examples = { @example (
+					value = "tTest([10.0,5.0,1.0, 3.0],[1.0,10.0,5.0,1.0])",
+					equals = "0.01") })
+	public static Double tTestPValue(final IScope scope, final IList seq1, final IList seq2) {
+		TTest t = new TTest();
+
+		double[] s1 = new double[seq1.length(scope)];
+		for (int i = 0; i < seq1.length(scope); i++) { s1[i] = Cast.asFloat(scope, seq1.get(i)); }
+
+		double[] s2 = new double[seq2.length(scope)];
+		for (int i = 0; i < seq2.length(scope); i++) { s2[i] = Cast.asFloat(scope, seq2.get(i)); }
+
+		return t.tTest(s1,s2);
+	}
 
 	@operator (
 			value = "dtw",