[Ifeffit] Purple & Red E Derivatives

[Andrew Korinda]

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