I sent this message to the maintainer's email address listed on the
signal package, but it bounced. Perhaps somebody on this list has more
insight into the signal package than I do (or knows the maintainer's new
address):
Subject:
question about buttord function in R signal module
From:
Michael Tiemann <michaeltiemann at mac.com>
Date:
Thu, 06 Nov 2008 07:18:58 -0500
To:
tshort at eprisolutions.com
Tom,
I was trying to compare lowpass and highpass filters and found that the
buttord example in the manual worked as expected, namely the $type was
"low". But when I reversed the Wp and Ws parameters, it resulted in
an
object with an empty $type instead of $type being "high". I looked at
the source code and found an obvious reason why:
if (length(Wp) == 2) {
warning("buttord seems to overdesign bandpass and bandreject
filters")
if (any(stop))
type = "stop"
else type = "pass"
}
else {
## here we set to "high" or "low", as expected
if (any(stop))
type = "high"
else type = "low"
}
## here we arbitrarily override the type if there is a stop band
defined...why?
if (any(stop))
type = ""
Thank you for any explanation you can provide.
M
