altoslib: Add user-selectable filter width for data smoothing

[fw/altos] / altoslib / AltosTimeSeries.java

diff --git a/altoslib/AltosTimeSeries.java b/altoslib/AltosTimeSeries.java
index 9f3b4d807ef26bb36ae9a358515ac41c17f3bad5..7208c176d1450678e324a29d8a591d10279d5668 100644 (file)
--- a/altoslib/AltosTimeSeries.java
+++ b/altoslib/AltosTimeSeries.java
@@ -20,15 +20,30 @@ public class AltosTimeSeries implements Iterable<AltosTimeValue>, Comparable<Alt
        public String                   label;
        public AltosUnits               units;
        ArrayList<AltosTimeValue>       values;
+       boolean                         data_changed;
 
        public int compareTo(AltosTimeSeries other) {
                return label.compareTo(other.label);
        }
 
        public void add(AltosTimeValue tv) {
+               data_changed = true;
                values.add(tv);
        }
 
+       public void erase_values() {
+               data_changed = true;
+               this.values = new ArrayList<AltosTimeValue>();
+       }
+
+       public void clear_changed() {
+               data_changed = false;
+       }
+
+//     public boolean changed() {
+//             return data_changed;
+//     }
+
        public void add(double time, double value) {
                add(new AltosTimeValue(time, value));
        }
@@ -264,14 +279,35 @@ public class AltosTimeSeries implements Iterable<AltosTimeValue>, Comparable<Alt
 
        }
 
-       private double filter_coeff(double dist, double width) {
-               double ratio = dist / (width / 2);
+       private static double i0(double x) {
+               double  ds = 1, d = 0, s = 0;
 
-               return Math.cos(ratio * Math.PI / 2);
+               do {
+                       d += 2;
+                       ds = ds * (x * x) / (d * d);
+                       s += ds;
+               } while (ds - 0.2e-8 * s > 0);
+               return s;
+       }
+
+       private static double kaiser(double n, double m, double beta) {
+               double alpha = m / 2;
+               double t = (n - alpha) / alpha;
+
+               if (t > 1)
+                       t = 1;
+               double k = i0 (beta * Math.sqrt (1 - t*t)) / i0(beta);
+               return k;
+       }
+
+       private double filter_coeff(double dist, double width) {
+               return kaiser(dist + width/2.0, width, 2 * Math.PI);
        }
 
        public AltosTimeSeries filter(AltosTimeSeries f, double width) {
+
                double  half_width = width/2;
+               int half_point = values.size() / 2;
                for (int i = 0; i < values.size(); i++) {
                        double  center_time = values.get(i).time;
                        double  left_time = center_time - half_width;