% -*- mode: noweb; noweb-default-code-mode: R-mode; -*-
\documentclass[a4paper,12pt,final]{article}
\usepackage{python}
\usepackage{graphicx}
\begin{document}

\title{Python Sweave Example \\ Frequency response of a moving average filter}
\author{Matti Pastell}

\maketitle

\textbf{Create 11 point moving average filter and plot its frequency response and print the values.}

<<engine=python>>=
from pylab import *
import scipy.signal as signal
#A function to plot frequency and phase response
def mfreqz(b,a=1):
    w,h = signal.freqz(b,a)
    h = abs(h)
    return(w/max(w), h)

#Make the impulse response function
n = 11.
b = repeat(1/n, n)
#Print impulse response filter
print(b)
@ 

\textbf{\\Calculate the frequency response and plot it:}

<<engine=python>>=
w, h = mfreqz(b)
#Plot the function
plot(w,h,'k')
ylabel('Amplitude')
xlabel(r'Normalized Frequency (x$\pi$rad/sample)')
title(r'Frequency response of an 11 point moving average filter')
savefig('ma_freq.pdf')
@ 

\includegraphics{ma_freq.pdf}


\end{document}