public void TestInterpolationPointReplacement()
{
IWriteableInterpolable interp = new SmallDoubleInterpolable(2);
IInterpolable interp2 = (IInterpolable)interp;
interp.SetYValue(3.3, 6.6);
interp.SetYValue(4.4, 8.8);
interp.SetYValue(7.7, 12.8);
interp.SetYValue(13.2, 22.8);
interp.SetYValue(7.7, 17.8);
Verify(interp2, 8.8, 18.8);
}
public void TestInterpolationFrom2Points()
{
IWriteableInterpolable interp = new SmallDoubleInterpolable(2);
IInterpolable interp2 = (IInterpolable)interp;
interp.SetYValue(3.3, 6.6);
interp.SetYValue(4.4, 8.8);
Verify(interp2, 5.5, 11);
Verify(interp2, 4.4, 8.8);
Verify(interp2, 3.85, 7.7);
Verify(interp2, 3.3, 6.6);
Verify(interp2, 2.2, 4.4);
Verify(interp2, 0.0, 0.0);
Verify(interp2, -2.2, -4.4);
}
public void TestInterpolationFrom4Points()
{
IWriteableInterpolable interp = new SmallDoubleInterpolable(4);
IInterpolable interp2 = (IInterpolable)interp;
interp.SetYValue(4.8, 2.7);
interp.SetYValue(3.2, 1.5);
interp.SetYValue(6.0, 4.5);
interp.SetYValue(0.8, 0.6);
Verify(interp2, 7.2, 6.3);
Verify(interp2, 6.0, 4.5);
Verify(interp2, 5.2, 3.3);
Verify(interp2, 4.8, 2.7);
Verify(interp2, 4.0, 2.1);
Verify(interp2, 3.2, 1.5);
Verify(interp2, 1.6, 0.9);
Verify(interp2, 0.8, 0.6);
Verify(interp2, 0.0, 0.3);
Verify(interp2, -0.8, 0.0);
}
/// <summary>
/// Given a list of source items, and a function that returns a double value for each, this
/// method ascertains the double value that represents the given percentile in that population.
/// For example, given a list of students, and a function that returns their grades, this method
/// will return the grade that represents the 50th percentile across that population of students.
/// </summary>
/// <typeparam name="T">The type of items in the list of source items.</typeparam>
/// <param name="srcItems">The source items for which we want to know the percentile.</param>
/// <param name="percentile">The percentile on the interval [0.0, 100.0] at which we seek the value from the source items.</param>
/// <param name="valueGetter">The function that ascertains the value of each source item.</param>
/// <param name="interpolate">if set to <c>true</c>, we interpolate between located items' values.</param>
/// <returns></returns>
public static double GetValueAtPercentile <T>(this List <T> srcItems, double percentile, Func <T, double> valueGetter, bool interpolate)
{
_Debug.Assert(srcItems.Count > 0, "Percentile was requested from a population of zero items. Percentile source populations must have at least one member.");
_Debug.Assert(percentile >= 0.0 && percentile <= 100.0, string.Format("Percentile was requested as {0} - it must be a double on the interval [0.0 ... 100.0]", percentile));
percentile = percentile / 100.0;
if (srcItems.Count == 1)
{
return(valueGetter(srcItems[0]));
}
else
{
srcItems.Sort((t1, t2) => Comparer <double> .Default.Compare(valueGetter(t1), valueGetter(t2)));
double index = (srcItems.Count - 1) * percentile;
double lowNdx = Math.Floor(index);
double hiNdx = Math.Ceiling(index);
if (lowNdx == hiNdx)
{
if (lowNdx == 0)
{
hiNdx++;
}
else
{
lowNdx--;
}
}
double lowVal = valueGetter(srcItems[(int)lowNdx]);
double hiVal = valueGetter(srcItems[(int)hiNdx]);
if (interpolate)
{
SmallDoubleInterpolable sdi = new SmallDoubleInterpolable(new[] { lowNdx, hiNdx }, new[] { lowVal, hiVal });
return(sdi.GetYValue(index));
}
else
{
return((index - lowNdx) < 0.5 ? lowVal : hiVal);
}
}
}
