matlab, filter function

Kenny Ortmann kortmann at ideaworks.com
Tue Oct 17 13:35:25 CDT 2006


just looking for some help, most of the time you guys are good with matlab 
code, i am trying to use the filter function under this setting

y = filter(b,a,X) filters the data in vector X with the filter described by 
numerator coefficient vector b and denominator coefficient vector a. If a(1) 
is not equal to 1, filter normalizes the filter coefficients by a(1). If 
a(1) equals 0, filter returns an error.

I pretty much have the same as the example, except my data array is 
different
data = [1:0.2:4]';
windowSize = 5;
filter(ones(1,windowSize)/windowSize,1,data)
ans =
    0.2000
    0.4400
    0.7200
    1.0400
    1.4000
    1.6000
    1.8000
    2.0000
    2.2000
    2.4000
    2.6000
    2.8000
    3.0000
    3.2000
    3.4000
    3.6000

my question is does numpy/scipy have a function for this, if not the 
algorithm states
y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb)
                 - a(2)*y(n-1) - ... - a(na+1)*y(n-na)but a is a number not 
an arrayThanks for the help,~Kenny 


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