public override FScheme.Value Evaluate(FSharpList <FScheme.Value> args)
{
if (!args[0].IsList)
{
throw new Exception("A list of XYZs is required to average.");
}
var lst = ((FScheme.Value.List)args[0]).Item;
var average = BestFitLine.MeanXYZ(BestFitLine.AsGenericList <XYZ>(lst));
return(FScheme.Value.NewContainer(average));
}