Skip to main content

Exploring Digital Filter Design with Python

If you analyze data chances are you need to use digital filters. The theory and practice of filter design and filter characteristics is well developed and requires some math background. If you do not have the patience to go through all the math the second best thing is to look at filter designs to get an intuition of how filter type and order translate into filter characteristics.

I've written a simple Python script using the Pylab and Scipy packages that allows you to interactively 'draw' a filter characteristic and see the filter design results from various algorithms.

The amplitude and phase characteristics, and the filter order are plotted and the coefficients are shown in the command window.

To play with this educational tool go to the neurapy repository on git hub and grab this script. Run in from ipython and explore the world of digital filter design.
Labels:

Comments

Post a Comment

Popular posts from this blog

A note on Python's __exit__() and errors

Python's context managers are a very neat way of handling code that needs a teardown once you are done. Python objects have do have a destructor method ( __del__ ) called right before the last instance of the object is about to be destroyed. You can do a teardown there. However there is a lot of fine print to the __del__ method. A cleaner way of doing tear-downs is through Python's context manager , manifested as the with keyword. class CrushMe: def __init__(self): self.f = open('test.txt', 'w') def foo(self, a, b): self.f.write(str(a - b)) def __enter__(self): return self def __exit__(self, exc_type, exc_val, exc_tb): self.f.close() return True with CrushMe() as c: c.foo(2, 3) One thing that is important, and that got me just now, is error handling. I made the mistake of ignoring all those 'junk' arguments ( exc_type, exc_val, exc_tb ). I just skimmed the docs and what popped out is that you need to return True or
Post a Comment
Read more

Using adminer on Mac OS X

adminer is a nice php based sqlite manager. I prefer the firefox plugin "sqlite manager" but it currently has a strange issue with FF5 that basically makes it unworkable, so I was looking for an alternative to tide me over. I really don't want apache running all the time on my computer and don't want people browsing to my computer, so what I needed to do was: Download the adminer php script into /Library/WebServer/Documents/ Change /etc/apache2/httpd.conf to allow running of php scripts (uncomment the line that begins: LoadModule php5_module Start the apache server: sudo apachectl -k start Operate the script by going to localhost Stop the server: sudo apachectl -k stop  
Post a Comment
Read more