Hi,

I am looking at the bandpass function after reading the black book. I get the general idea of the function however am still confused by the parameters.

The paragraph below is copied from the book.


vars Cycles = series(BandPass(Prices,30,2));

The behavior of a bandpass filter can be seen in the second curve of Fig. 15 in the previous chapter. Its function is similar to a lowpass filter except that it dampens not only low but also high frequencies, i.e. short cycles. This bandpass filter has a center period of 30 bars and a width of 2 (the width determines the frequency range that can pass the filter). This way the trend (a cycle with a very long period) and the noise (short period cycles) are removed from the price curve. The result is a clean curve that consists mostly of the peaks and valleys of the 30-bars cycle,

If someone could give more information on the 30 parameter & the width of 2 parameter. As I don't understand what the two really means even though it mentions it determines the frequency range.

Thanks for any help!