matrix: imported matrix as a subtree

matrix/mat64/format_example_test.go

@@ -0,0 +1,112 @@
+// Copyright ©2015 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 mat64_test
+
+import (
+	"fmt"
+
+	"github.com/gonum/matrix/mat64"
+)
+
+func ExampleFormatted() {
+	a := mat64.NewDense(3, 3, []float64{1, 2, 3, 0, 4, 5, 0, 0, 6})
+
+	// Create a matrix formatting value with a prefix and calculating each column
+	// width individually...
+	fa := mat64.Formatted(a, mat64.Prefix("    "), mat64.Squeeze())
+
+	// and then print with and without zero value elements.
+	fmt.Printf("with all values:\na = %v\n\n", fa)
+	fmt.Printf("with only non-zero values:\na = % v\n\n", fa)
+
+	// Modify the matrix...
+	a.Set(0, 2, 0)
+
+	// and print it without zero value elements.
+	fmt.Printf("after modification with only non-zero values:\na = % v\n\n", fa)
+
+	// Modify the matrix again...
+	a.Set(0, 2, 123.456)
+
+	// and print it using scientific notation for large exponents.
+	fmt.Printf("after modification with scientific notation:\na = %.2g\n\n", fa)
+	// See golang.org/pkg/fmt/ floating-point verbs for a comprehensive list.
+
+	// Output:
+	// with all values:
+	// a = ⎡1  2  3⎤
+	//     ⎢0  4  5⎥
+	//     ⎣0  0  6⎦
+	//
+	// with only non-zero values:
+	// a = ⎡1  2  3⎤
+	//     ⎢.  4  5⎥
+	//     ⎣.  .  6⎦
+	//
+	// after modification with only non-zero values:
+	// a = ⎡1  2  .⎤
+	//     ⎢.  4  5⎥
+	//     ⎣.  .  6⎦
+	//
+	// after modification with scientific notation:
+	// a = ⎡1  2  1.2e+02⎤
+	//     ⎢0  4        5⎥
+	//     ⎣0  0        6⎦
+}
+
+func ExampleExcerpt() {
+	// Excerpt allows diagnostic display of very large
+	// matrices and vectors.
+
+	// The big matrix is too large to properly print...
+	big := mat64.NewDense(100, 100, nil)
+	for i := 0; i < 100; i++ {
+		big.Set(i, i, 1)
+	}
+
+	// so only print corner excerpts of the matrix.
+	fmt.Printf("excerpt big identity matrix: %v\n\n",
+		mat64.Formatted(big, mat64.Prefix(" "), mat64.Excerpt(3)))
+
+	// The long vector is also too large, ...
+	long := mat64.NewVector(100, nil)
+	for i := 0; i < 100; i++ {
+		long.SetVec(i, float64(i))
+	}
+
+	// ... so print end excerpts of the vector,
+	fmt.Printf("excerpt long column vector: %v\n\n",
+		mat64.Formatted(long, mat64.Prefix(" "), mat64.Excerpt(3)))
+	// or its transpose.
+	fmt.Printf("excerpt long row vector: %v\n",
+		mat64.Formatted(long.T(), mat64.Prefix(" "), mat64.Excerpt(3)))
+
+	// Output:
+	// excerpt big identity matrix: Dims(100, 100)
+	//  ⎡1  0  0  ...  ...  0  0  0⎤
+	//  ⎢0  1  0            0  0  0⎥
+	//  ⎢0  0  1            0  0  0⎥
+	//   .
+	//   .
+	//   .
+	//  ⎢0  0  0            1  0  0⎥
+	//  ⎢0  0  0            0  1  0⎥
+	//  ⎣0  0  0  ...  ...  0  0  1⎦
+	//
+	// excerpt long column vector: Dims(100, 1)
+	//  ⎡ 0⎤
+	//  ⎢ 1⎥
+	//  ⎢ 2⎥
+	//   .
+	//   .
+	//   .
+	//  ⎢97⎥
+	//  ⎢98⎥
+	//  ⎣99⎦
+	//
+	// excerpt long row vector: Dims(1, 100)
+	//  [ 0   1   2  ...  ...  97  98  99]
+
+}