So just a few things, first of all you can use a foreach loop or even just AddRange over what you're currently doing (and it's less bug prone):
Alternatively:
Both require _resampledPoints to be an IEnumerable<DataPoint> collection.
Second, please provide the code you use to assign the horizontal axis (or just all of them) to the PlotModel, can't really help when you're just adding points to a series =P.
foreach (var p in _resampledPoints) tmp.Points.Add(p);
tmp.Points.AddRange(_resampledPoints);
Second, please provide the code you use to assign the horizontal axis (or just all of them) to the PlotModel, can't really help when you're just adding points to a series =P.