Hey John,
Just to make sure I understand, you are setting the axismode to autoscaleexact, and some of the data points are outside of the plot area? I tried creating a very simple example here, and I didn't seem to have a problem. Would it be possible to post a small example that demonstrates this behavior so I could take a look at it here? One other thing might be to try autoscaleloose to see if this shows the same behavior for you.
Pat P.
Software Engineer
National Instruments