# frequency transformation for filter design

Started by April 29, 2009
Hello,

I am designing some bandpass filters, starting from a normalized low-pass Butterworth approximation.
I have the nominator and the denominator of the transfer function.
With:
tf(nom,den);
I get the transfer function. How can I change the variable s to variable s1=Q*(s/w+w/s)?

On the other hand, how can I change the order of teh values in a vector? For example if I have vector A=[1 2 3] how can I get B=[ 3 2 1]

thanks a lot,
Paul
I do not understand the question but if you want change

V=[a b c d e f] in W = [f e d c b a]
you can use flip left to right
W = fliplr(V)

or if you have V = [a b c d e f] ' (this is a column vector)
flip up down
W = fplipud(V)
On 4/28/09, f...@yahoo.co.uk wrote:
> Hello,
>
> I am designing some bandpass filters, starting from a normalized low-pass
> Butterworth approximation.
> I have the nominator and the denominator of the transfer function.
> With:
> tf(nom,den);
> I get the transfer function. How can I change the variable s to variable
> s1=Q*(s/w+w/s)?
>
> On the other hand, how can I change the order of teh values in a vector? For
> example if I have vector A=[1 2 3] how can I get B=[ 3 2 1]
>
> thanks a lot,
> Paul
>