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Had to reimplement getValue to not use TreeMap/SortedMap apis unavailable in Froyo. Added some comments so it should be easier to read. Test cases continue to pass.

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This commit is contained in:
Kevin Ruland 2012-07-19 14:45:48 +00:00
parent 51f98b71aa
commit 52f0e0cf90
1 changed files with 61 additions and 36 deletions
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59
core/src/net/sf/openrocket/util/LinearInterpolator.java
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@ -1,7 +1,7 @@
package net.sf.openrocket.util; package net.sf.openrocket.util;
import java.util.Iterator; import java.util.Iterator;
import java.util.Map; import java.util.SortedMap;
import java.util.TreeMap; import java.util.TreeMap;
public class LinearInterpolator implements Cloneable { public class LinearInterpolator implements Cloneable {
@ -60,32 +60,57 @@ public class LinearInterpolator implements Cloneable {
public double getValue(double x) { public double getValue(double x) {
Map.Entry<Double,Double> e1, e2;
double x1, x2; double x1, x2;
double y1, y2; Double y1, y2;
// Froyo does not support floorEntry, firstEntry or higherEntry. We instead have to
// resort to using other more awkward methods.
e1 = sortMap.floorEntry(x); y1 = sortMap.get(x);
if (e1 == null) { if ( y1 != null ) {
// x smaller than any value in the set // Wow, x was a key in the map. Such luck.
e1 = sortMap.firstEntry(); return y1.doubleValue();
if (e1 == null) { }
// we now know that x is not in the map, so we need to find the lower and higher keys.
// let's just make certain that our map is not empty.
if ( sortMap.isEmpty() ) {
throw new IllegalStateException("No points added yet to the interpolator."); throw new IllegalStateException("No points added yet to the interpolator.");
} }
return e1.getValue();
// firstKey in the map - cannot be null since the map is not empty.
Double firstKey = sortMap.firstKey();
// x is smaller than the first entry in the map.
if ( x < firstKey.doubleValue() ) {
y1 = sortMap.get(firstKey);
return y1.doubleValue();
} }
x1 = e1.getKey(); // floor key is the largest key smaller than x - since we have at least one key,
e2 = sortMap.higherEntry(x1); // and x>=firstKey, we know that floorKey != null.
Double floorKey = sortMap.subMap(firstKey, x).lastKey();
if (e2 == null) { x1 = floorKey.doubleValue();
// x larger than any value in the set y1 = sortMap.get(floorKey);
return e1.getValue();
// Now we need to find the key that is greater or equal to x
SortedMap<Double,Double> tailMap = sortMap.tailMap(x);
// Check if x is bigger than all the entries.
if ( tailMap.isEmpty() ) {
return y1.doubleValue();
}
Double ceilKey = tailMap.firstKey();
// Check if x is bigger than all the entries.
if ( ceilKey == null ) {
return y1.doubleValue();
} }
x2 = e2.getKey(); x2 = ceilKey.doubleValue();
y1 = e1.getValue(); y2 = sortMap.get(ceilKey);
y2 = e2.getValue();
return (x - x1)/(x2-x1) * (y2-y1) + y1; return (x - x1)/(x2-x1) * (y2-y1) + y1;
} }