How to apply a notch filter in frequency domain data?

Hi,

I am new in filters. I have a time domain curve and would like to implement a notch (or similar) filter in the frequency domain of this curve. My aim is to keep in the low and high frequency components of the signal and filter out 1/2 or 1/3 of the amplitude of the middle frequency components. In other words, I would like to filter out some important noise from my signal.

I tried to use f.design.notch but with no success yet. Any ideas?

I would appreciate your help.

G

[George Papas]

Just to add some additional information to my previous question which can clarify further:

I would like to filter out 1/2 or 1/3 of the amplitudes of the frequency components whithin the orthogonal area of the following image:

https://www.dropbox.com/s/r6p57oj0cacjpoq/La%20place%20domain%20of%20signal%20intensity%20curves.jpg