correct weighted test, and make fixture clearer

Changed the names of the test table to be clearer.  Also made the
answer a matrix and used Dense.Equals instead of performing the
comparison on r, c, and the raw data.

Also, the old results for the weighted case were wrong.  I’ve added the
same items into the stat_test.go file.

covariancematrix_test.go

@@ -9,7 +9,6 @@ import (
 	"testing"
 
 	"github.com/gonum/blas/goblas"
-	"github.com/gonum/floats"
 	"github.com/gonum/matrix/mat64"
 )
 
@@ -18,14 +17,16 @@ func init() {
 }
 
 func TestCovarianceMatrix(t *testing.T) {
+
+	// An alternate way to test this is to call the Variance
+	// and Covariance functions and ensure that the results are identical.
 	for i, test := range []struct {
-		mat     mat64.Matrix
+		data    mat64.Matrix
 		weights mat64.Vec
-		r, c    int
-		x       []float64
+		ans     mat64.Matrix
 	}{
 		{
-			mat: mat64.NewDense(5, 2, []float64{
+			data: mat64.NewDense(5, 2, []float64{
 				-2, -4,
 				-1, 2,
 				0, 0,
@@ -33,65 +34,30 @@ func TestCovarianceMatrix(t *testing.T) {
 				2, 4,
 			}),
 			weights: nil,
-			r:       2,
-			c:       2,
-			x: []float64{
+			ans: mat64.NewDense(2, 2, []float64{
 				2.5, 3,
 				3, 10,
-			},
+			}),
 		}, {
-			mat: mat64.NewDense(5, 2, []float64{
-				-2, -4,
-				-1, 2,
-				0, 0,
-				1, -2,
+			data: mat64.NewDense(3, 2, []float64{
+				1, 1,
 				2, 4,
+				3, 9,
 			}),
 			weights: []float64{
+				1,
 				1.5,
-				.5,
-				1.5,
-				.5,
 				1,
 			},
-			r: 2,
-			c: 2,
-			x: []float64{
-				2.75, 4.5,
-				4.5, 11,
-			},
-		}, {
-			mat: mat64.NewDense(5, 2, []float64{
-				-2, -4,
-				-1, 2,
-				0, 0,
-				1, -2,
-				2, 4,
+			ans: mat64.NewDense(2, 2, []float64{
+				.8, 3.2,
+				3.2, 13.142857142857146,
 			}),
-			weights: mat64.Vec([]float64{
-				1.5,
-				.5,
-				1.5,
-				.5,
-				1,
-			}),
-			r: 2,
-			c: 2,
-			x: []float64{
-				2.75, 4.5,
-				4.5, 11,
-			},
 		},
 	} {
-		c := CovarianceMatrix(nil, test.mat, test.weights).RawMatrix()
-		if c.Rows != test.r {
-			t.Errorf("%d: expected rows %d, found %d", i, test.r, c.Rows)
-		}
-		if c.Cols != test.c {
-			t.Errorf("%d: expected cols %d, found %d", i, test.c, c.Cols)
-		}
-		if !floats.Equal(test.x, c.Data) {
-			t.Errorf("%d: expected data %#q, found %#q", i, test.x, c.Data)
+		c := CovarianceMatrix(nil, test.data, test.weights)
+		if !c.Equals(test.ans) {
+			t.Errorf("%d: expected cov %v, found %v", i, test.ans, c)
 		}
 	}
 	if !Panics(func() { CovarianceMatrix(nil, mat64.NewDense(5, 2, nil), mat64.Vec([]float64{})) }) {