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Improved efficiency. 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141234 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Phil Steitz 2004-05-22 19:59:22 +00:00
parent 092b61c11f
commit 384e07ad45
1 changed files with 7 additions and 13 deletions
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20
src/java/org/apache/commons/math/analysis/SplineInterpolator.java
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@ -39,7 +39,7 @@ import java.io.Serializable;
* The cubic spline interpolation algorithm implemented is as described in R.L. Burden, J.D. Faires,
* <u>Numerical Analysis</u>, 4th Ed., 1989, PWS-Kent, ISBN 0-53491-585-X, pp 126-131.
*
* @version $Revision: 1.16 $ $Date: 2004/04/27 04:37:58 $
* @version $Revision: 1.17 $ $Date: 2004/05/22 19:59:22 $
*
*/
public class SplineInterpolator implements UnivariateRealInterpolator, Serializable {
@ -69,27 +69,22 @@ public class SplineInterpolator implements UnivariateRealInterpolator, Serializa
}
}
// Differences between knot points
double h[] = new double[n];
for (int i = 0; i < n; i++) {
h[i] = x[i + 1] - x[i];
}
double alpha[] = new double[n];
for (int i = 1; i < n; i++) {
alpha[i] = 3d * (y[i + 1] * h[i - 1] - y[i] * (x[i + 1] - x[i - 1])+ y[i - 1] * h[i]) /
(h[i - 1] * h[i]);
}
double l[] = new double[n + 1];
double mu[] = new double[n];
double z[] = new double[n + 1];
l[0] = 1d;
mu[0] = 0d;
z[0] = 0d;
double g = 0;
for (int i = 1; i < n; i++) {
l[i] = 2d * (x[i+1] - x[i - 1]) - h[i - 1] * mu[i -1];
mu[i] = h[i] / l[i];
z[i] = (alpha[i] - h[i - 1] * z[i - 1]) / l[i];
g = 2d * (x[i+1] - x[i - 1]) - h[i - 1] * mu[i -1];
mu[i] = h[i] / g;
z[i] = (3d * (y[i + 1] * h[i - 1] - y[i] * (x[i + 1] - x[i - 1])+ y[i - 1] * h[i]) /
(h[i - 1] * h[i]) - h[i - 1] * z[i - 1]) / g;
}
// cubic spline coefficients -- b is linear, c quadratic, d is cubic (original y's are constants)
@ -97,7 +92,6 @@ public class SplineInterpolator implements UnivariateRealInterpolator, Serializa
double c[] = new double[n + 1];
double d[] = new double[n];
l[n] = 1d;
z[n] = 0d;
c[n] = 0d;