private static void pwl_value_1d_test()
//****************************************************************************80
//
// Purpose:
//
// PWL_VALUE_1D_TEST tests PWL_VALUE_1D.
//
// Discussion:
//
// f(x) = x^3 - 12 x^2 + 39 x - 28 = ( x - 1 ) * ( x - 4 ) * ( x - 7 )
//
// Licensing:
//
// This code is distributed under the GNU LGPL license.
//
// Modified:
//
// 01 July 2015
//
// Author:
//
// John Burkardt
//
{
const int nd = 4;
const int ni = 21;
double[] xd = { 0.0, 2.0, 5.0, 10.0 };
double[] yd = { -28.0, +10.0, -8.0, +162.0 };
Console.WriteLine("");
Console.WriteLine("PWL_VALUE_1D_TEST:");
Console.WriteLine(" PWL_VALUE_1D evaluates a piecewise linear 1D interpolant.");
const double x_min = 0.0;
const double x_max = 10.0;
double[] xi = typeMethods.r8vec_linspace_new(ni, x_min, x_max);
double[] yi = Interp1D.pwl_value_1d(nd, xd, yd, ni, xi);
typeMethods.r8vec2_print(ni, xi, yi, " Table of interpolant values:");
}
private static void pwl_basis_1d_test()
//****************************************************************************80
//
// Purpose:
//
// PWL_BASIS_1D_TEST tests PWL_BASIS_1D.
//
// Licensing:
//
// This code is distributed under the GNU LGPL license.
//
// Modified:
//
// 01 July 2015
//
// Author:
//
// John Burkardt
//
{
const int nd = 4;
const int ni = 21;
double[] xd = { 0.0, 2.0, 5.0, 10.0 };
Console.WriteLine("");
Console.WriteLine("PWL_BASIS_1D_TEST:");
Console.WriteLine(" PWL_BASIS_1D evaluates the piecewise linear 1D basis");
Console.WriteLine(" functions.");
const double x_min = 0.0;
const double x_max = 10.0;
double[] xi = typeMethods.r8vec_linspace_new(ni, x_min, x_max);
double[] lb = Interp1D.pwl_basis_1d(nd, xd, ni, xi);
typeMethods.r8mat_print(ni, nd, lb, " The piecewise linear basis functions:");
}
private static void pwl_interp_1d_test01(int prob)
//****************************************************************************80
//
// Purpose:
//
// PWL_INTERP_1D_TEST01 tests PWL_INTERP_1D.
//
// Licensing:
//
// This code is distributed under the GNU LGPL license.
//
// Modified:
//
// 31 May 2013
//
// Author:
//
// John Burkardt
//
// Parameters:
//
// Input, int PROB, the problem index.
//
{
List <string> command_unit = new();
List <string> data_unit = new();
int i;
List <string> interp_unit = new();
int j;
Console.WriteLine("");
Console.WriteLine("PWL_INTERP_1D_TEST01:");
Console.WriteLine(" PWL_INTERP_1D evaluates the piecewise linear interpolant.");
Console.WriteLine(" Interpolate data from TEST_INTERP problem #" + prob + "");
int nd = TestInterp.p00_data_num(prob);
Console.WriteLine(" Number of data points = " + nd + "");
double[] xy = TestInterp.p00_data(prob, 2, nd);
typeMethods.r8mat_transpose_print(2, nd, xy, " Data array:");
double[] xd = new double[nd];
double[] yd = new double[nd];
for (i = 0; i < nd; i++)
{
xd[i] = xy[0 + 2 * i];
yd[i] = xy[1 + 2 * i];
}
//
// #1: Does interpolant match function at interpolation points?
//
int ni = nd;
double[] xi = new double[ni];
for (i = 0; i < ni; i++)
{
xi[i] = xd[i];
}
double[] yi = Interp1D.pwl_value_1d(nd, xd, yd, ni, xi);
double interp_error = typeMethods.r8vec_diff_norm(ni, yi, yd) / ni;
Console.WriteLine("");
Console.WriteLine(" L2 interpolation error averaged per interpolant node = " + interp_error + "");
//
// Create data file.
//
string data_filename = "data" + prob + ".txt";
for (j = 0; j < nd; j++)
{
data_unit.Add(" " + xd[j]
+ " " + yd[j] + "");
}
File.WriteAllLines(data_filename, data_unit);
Console.WriteLine("");
Console.WriteLine(" Created graphics data file \"" + data_filename + "\".");
//
// Create interp file.
//
ni = 501;
double xmin = typeMethods.r8vec_min(nd, xd);
double xmax = typeMethods.r8vec_max(nd, xd);
xi = typeMethods.r8vec_linspace_new(ni, xmin, xmax);
yi = Interp1D.pwl_value_1d(nd, xd, yd, ni, xi);
string interp_filename = "interp" + prob + ".txt";
for (j = 0; j < ni; j++)
{
interp_unit.Add(" " + xi[j]
+ " " + yi[j] + "");
}
File.WriteAllLines(interp_filename, interp_unit);
Console.WriteLine(" Created graphics interp file \"" + interp_filename + "\".");
//
// Plot the data and the interpolant.
//
string command_filename = "commands" + prob + ".txt";
string output_filename = "plot" + prob + ".png";
command_unit.Add("# " + command_filename + "");
command_unit.Add("#");
command_unit.Add("# Usage:");
command_unit.Add("# gnuplot < " + command_filename + "");
command_unit.Add("#");
command_unit.Add("set term png");
command_unit.Add("set output '" + output_filename + "'");
command_unit.Add("set xlabel '<---X--->'");
command_unit.Add("set ylabel '<---Y--->'");
command_unit.Add("set title 'Data versus Nearest Neighbor Interpolant'");
command_unit.Add("set grid");
command_unit.Add("set style data lines");
command_unit.Add("plot '" + data_filename
+ "' using 1:2 with points pt 7 ps 2 lc rgb 'blue',\\");
command_unit.Add(" '" + interp_filename
+ "' using 1:2 lw 3 linecolor rgb 'red'");
File.WriteAllLines(command_filename, command_unit);
Console.WriteLine(" Created graphics command file \"" + command_filename + "\".");
}
