mat: add examples for Col and Row

mat/matrix_example_test.go

@@ -0,0 +1,43 @@
+// Copyright ©2019 The Gonum Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package mat_test
+
+import (
+	"fmt"
+
+	"gonum.org/v1/gonum/mat"
+)
+
+func ExampleCol() {
+	// This example copies the second column of a matrix into col, allocating a new slice of float64.
+	m := mat.NewDense(3, 3, []float64{
+		2.0, 9.0, 3.0,
+		4.5, 6.7, 8.0,
+		1.2, 3.0, 6.0,
+	})
+
+	col := mat.Col(nil, 1, m)
+
+	fmt.Printf("col = %#v", col)
+	// Output:
+	//
+	// col = []float64{9, 6.7, 3}
+}
+
+func ExampleRow() {
+	// This example copies the third row of a matrix into row, allocating a new slice of float64.
+	m := mat.NewDense(3, 3, []float64{
+		2.0, 9.0, 3.0,
+		4.5, 6.7, 8.0,
+		1.2, 3.0, 6.0,
+	})
+
+	row := mat.Row(nil, 2, m)
+
+	fmt.Printf("row = %#v", row)
+	// Output:
+	//
+	// row = []float64{1.2, 3, 6}
+}