If Count Expression

[ltc]

I need help with a formula that I've been given. 

=Aggr(

  If(count([filename]) <= 10, Dual('0-10 Times', 0),

  If(count([filename]) > 10 and count([filename]) <= 30, Dual('11-30 Times', 1),

  If(count([filename]) > 30 and count([filename]) <= 50, Dual('31-50 Times', 2),

  If(count([filename]) > 50, Dual('50+ Times', 3)))))

, [filename])

I use this formula for the following bar chart:

Now, if I make a selection and on this bar chart, for lets say, 31-50 Times, this works.  I get this result:

Problem: if I make a selection on the pie chart, for lets say, 2018, the bar chart selection changes:

The bar chart selections removed the column for 31-50 Times and is providing two other columns instead.  Instead, I would expect no columns shown on the bar chart because there are no longer any filenames in 2018 that were used 31-50 Times.

I understand why it's giving me these results - because it filtered for the "Filename" and not for "31-50 Times":

How can I adjust the formula to fix this problem?

Thank you!