### 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.

### Python: Multiprocessing: passing multiple arguments to a function

Write a wrapper function to unpack the arguments before calling the real function. Lambda won't work, for some strange un-Pythonic reason.

import multiprocessing as mp def myfun(a,b): print a + b def mf_wrap(args): return myfun(*args) p = mp.Pool(4) fl = [(a,b) for a in range(3) for b in range(2)] #mf_wrap = lambda args: myfun(*args) -> this sucker, though more pythonic and compact, won't work p.map(mf_wrap, fl)

### Flowing text in inkscape (Poster making)

You can flow text into arbitrary shapes in inkscape. (From a hint here).

You simply create a text box, type your text into it, create a frame with some drawing tool, select both the text box and the frame (click and shift) and then go to text->flow into frame.

UPDATE:

Trying to enter sentence so that text forms the number three...any ideas?
The solution:
Type '3' using the text toolConvert to path using object->pathSize as necessaryRemove fillUngroupType in actual text in new text boxSelect the text and the '3' pathFlow the text

### Latex math: Vertical bar

Like that used for indicating the evaluation of integrals between limits:

\bigg|

as in

\frac{\rho}{4\pi}\left(-\frac{1}{r}\right)\bigg|_{r_{0}}^{\infty}

from a hint here from robphy