matrix/mat64: reverse API signatures for matrix extraction

matrix/mat64/hogsvd_example_test.go

@@ -25,14 +25,14 @@ func ExampleHOGSVD() {
 
 	for i, n := range []string{"Africa", "Asia", "Latin America/Caribbean", "Oceania"} {
 		var u mat64.Dense
-		u.UFromHOGSVD(&gsvd, i)
+		gsvd.UTo(&u, i)
 		s := gsvd.Values(nil, i)
 		fmt.Printf("%s\n\ts_%d = %.4f\n\n\tU_%[2]d = %.4[4]f\n",
 			n, i, s, mat64.Formatted(&u, mat64.Prefix("\t      ")))
 	}
 
 	var v mat64.Dense
-	v.VFromHOGSVD(&gsvd)
+	gsvd.VTo(&v)
 	fmt.Printf("\nCommon basis vectors\n\n\tV^T = %.4f",
 		mat64.Formatted(v.T(), mat64.Prefix("\t      ")))