1 /*
2 * ZSegmentFit.java
3 *
4 * Created on August 1, 2007, 9:46 AM
5 *
6 */
7
8 package org.lcsim.fit.zsegment;
9
10 import java.util.List;
11 import hep.physics.matrix.SymmetricMatrix;
12
13 /**
14 * Encapsulates the constraints in the z0 - tan(lambda) track parameters
15 * due to a track passing through a set of detectors segmented in z.
16 * @author Richard Partridge
17 * @version 1.0
18 */
19 public class ZSegmentFit {
20
21 private List<double[]> _polygon;
22 private double[] _centroid;
23 private SymmetricMatrix _covariance;
24
25 /**
26 * Create a new instance of ZSegmentFit
27 * @param polygon List of vertices of the polygon describing the allowed region in the z0 - tan(lambda) plane.
28 * Each vertex is a double[2] with the first element being the z0 coordinate and the second
29 * the tan(lambda) coordinate.
30 * @param centroid Centroid of the polygon, where centroid[0] is the z0 coordinate, centroid[1] is the tan(lambda) coordinate
31 * @param covariance Covariance matrix calculated assuming equal probability for all points in the polygonal allowed region
32 */
33 public ZSegmentFit(List<double[]> polygon, double[] centroid, SymmetricMatrix covariance) {
34 _polygon = polygon;
35 _centroid = centroid;
36 _covariance = covariance;
37 }
38
39 /**
40 * Return the polygon that specifies the allowed region in z0 - tan(lambda) space
41 * @return List of vertices for the polygon. Each vertex is returned as a double[2] with the first element
42 * giving the z0 coordinate and the second element the tan(lambda) coordinate
43 */
44 public List<double[]> getPolygon() {
45 return _polygon;
46 }
47
48 /**
49 * Return the centroid (i.e., center of gravity) of the allowed region in the z0-tan(lambda) plane
50 * @return Centroid of the polygon, with the first element giving the z0 coordinate and the second element
51 * giving the tan(lambda) coordinate
52 */
53 public double[] getCentroid() {
54 return _centroid;
55 }
56
57 /**
58 * Return the covariance matrix for the allowed region in the z0 - tan(lambda) plane
59 * @return Covariance matrix
60 */
61 public SymmetricMatrix getCovariance() {
62 return _covariance;
63 }
64
65 /**
66 * Return a string containing properties of this ZSegmentFit
67 * @return String containing ZSegmentFit properties
68 */
69 public String toString() {
70 String nl = System.getProperty("line.separator");
71 StringBuffer output = new StringBuffer("ZSegmentFit: Centroid (z0, tan(lambda)) = ("+_centroid[0]+", "+_centroid[1]+")"+nl);
72 output.append(" Covariance matrix ("+_covariance.e(0,0)+", "+_covariance.e(1,0)+", "+_covariance.e(1,1)+")"+nl);
73 output.append(" Allowed region is a "+_polygon.size()+" sided polygon with vertices:"+nl);
74 for (double[] vert : _polygon) {
75 output.append(" ("+vert[0]+", "+vert[1]+")"+nl);
76 }
77 return new String(output);
78 }
79
80 }