Improved single sine wave function to handle cutoff value problems

src/main/java/no/nibio/vips/model/maths/NonLinearCurves.java

@@ -132,7 +132,7 @@ public class NonLinearCurves {
         Double theta_2 = Math.asin((Tu - m) / alpha);
         
         // Case 5: Tmin above Tl and Tmax above Tu
-        if(Tmin >= Tl && Tu != null && Tmax >= Tu)
+        if(Tmin > Tl && Tu != null && Tmax > Tu)
         {
             return (1/Math.PI) * ( 
                     (m-Tl)*(theta_2 + Math.PI/2) 

src/test/java/no/nibio/vips/model/maths/NonLinearCurvesTest.java

@@ -190,6 +190,14 @@ public class NonLinearCurvesTest extends TestCase {
         result = instance.calculateSingleSineWaveWithCutoff(tMin, tMax, thresholdLower, thresholdUpper);
         assertEquals(expectedResult, result,0.1);
         
+        tMax = 32.0;
+        tMin = 20.0;
+        thresholdUpper = 31.1;
+        thresholdLower = 20.0;
+        expectedResult = 5.894588543400416;
+        result = instance.calculateSingleSineWaveWithCutoff(tMin, tMax, thresholdLower, thresholdUpper);
+        assertEquals(expectedResult, result,0.1);
+        
     }
     
 }