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Ingy döt Net 2023-07-01 11:58:00 -04:00
parent 72d218235f
commit f23f22d71c
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55
Task/Thieles-interpolation-formula/Java/thieles-interpolation-formula.java Normal file
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import static java.lang.Math.*;
public class Test {
final static int N = 32;
final static int N2 = (N * (N - 1) / 2);
final static double STEP = 0.05;
static double[] xval = new double[N];
static double[] t_sin = new double[N];
static double[] t_cos = new double[N];
static double[] t_tan = new double[N];
static double[] r_sin = new double[N2];
static double[] r_cos = new double[N2];
static double[] r_tan = new double[N2];
static double rho(double[] x, double[] y, double[] r, int i, int n) {
if (n < 0)
return 0;
if (n == 0)
return y[i];
int idx = (N - 1 - n) * (N - n) / 2 + i;
if (r[idx] != r[idx])
r[idx] = (x[i] - x[i + n])
/ (rho(x, y, r, i, n - 1) - rho(x, y, r, i + 1, n - 1))
+ rho(x, y, r, i + 1, n - 2);
return r[idx];
}
static double thiele(double[] x, double[] y, double[] r, double xin, int n) {
if (n > N - 1)
return 1;
return rho(x, y, r, 0, n) - rho(x, y, r, 0, n - 2)
+ (xin - x[n]) / thiele(x, y, r, xin, n + 1);
}
public static void main(String[] args) {
for (int i = 0; i < N; i++) {
xval[i] = i * STEP;
t_sin[i] = sin(xval[i]);
t_cos[i] = cos(xval[i]);
t_tan[i] = t_sin[i] / t_cos[i];
}
for (int i = 0; i < N2; i++)
r_sin[i] = r_cos[i] = r_tan[i] = Double.NaN;
System.out.printf("%16.14f%n", 6 * thiele(t_sin, xval, r_sin, 0.5, 0));
System.out.printf("%16.14f%n", 3 * thiele(t_cos, xval, r_cos, 0.5, 0));
System.out.printf("%16.14f%n", 4 * thiele(t_tan, xval, r_tan, 1.0, 0));
}
}