While working in Athena today I noticed something peculiar while looking at the derivative plots of mu(E) data. When I plot the current group (red button) the plot can be spiky. However, when I plot as marked group (purple button) everything is much smoother and more rounded. Smoothed data will do the same thing. It always happens whether I have mu(E) or norm(E) selected. I have never noticed a difference in how any of the other plots current when switching between marked and active plotting. I didn't see anything in the documentation about how the derivatives are calculated so I'm turning to all of you. Have any of you noticed this? Does anyone know if there is a difference in how the derivatives are calculated in each plotting function? Andy Korinda Notestein Lab Northwestern University