What is the value of the object to be parsed (the argument of the ToDouble) method. To me the code looks OK, and it should always be possible to convert double to double...

You can create a custom Annotation class to draw anything you want in the plot view.
Also see the `DelegateAnnotation` in the `ExampleLibrary.RenderingCapabilities` class, that is very general.

Sorry, I tried to format your code example, but the code was deleted instead... Can you post the code again?

This sounds like a bug, please add it to the GitHub issues.
It could be related to #59, but that's a new feature, I think.

Did you see the examples in https://github.com/oxyplot/oxyplot/tree/develop/Source/Examples/WPF/WpfExamples/Examples/RealtimeDemo

I don't think 1250 points at 4 Hz should be a problem.

We are currently only testing with Xamarin.Android, sorry I am not sure how it currently works with MonoDroid.

I think you should do the filtering in your code, then set the `ItemsSource` of the `LineSeries` to the filtered collection.

I think you could export to png and then use PresentationML in the OpenXML SDK to export to Powerpoint!

I remember doing this with imagetools long time ago. See http://blogs.msdn.com/b/kirillosenkov/archive/2009/10/12/saving-images-bmp-png-etc-in-wpf-silverlight.aspx
I don´t know if there are better ways to do this in Silverlight 5...

There is simple pdf export in the portable library. http://oxyplot.org/documentation/export-pdf
I don´t think png export is implemented for Xamarin Forms yet, that´s a feature that should be added to the GitHub issues!
The iOS implementation has simple png export. On iOS it should also be possible to export to pdf with core graphics, I think.
The Android implementation has no png export yet.