def deci24(x):
<EOL>b2,a2 = signal.butter(<NUM_LIT:10>,<NUM_LIT:1>/<NUM_LIT>)<EOL>y1 = signal.lfilter(b2,a2,x)<EOL>y1 = downsample(y1,<NUM_LIT:2>)<EOL>b3,a3 = signal.butter(<NUM_LIT:10>,<NUM_LIT:1>/<NUM_LIT>)<EOL>y2 = signal.lfilter(b3,a3,y1)<EOL>y2 = downsample(y2,<NUM_LIT:3>)<EOL>b4,a4 = signal.butter(<NUM_LIT:10>,<NUM_LIT:1>/<NUM_LIT>)<EOL>y3 = signal.lfilter(b4,a4,y2)<EOL>y3 = downsample(y3,<NUM_LIT:4>)<EOL>return y3<EOL>
Decimate by L = 24 using Butterworth filters.

The decimation is done using two three stages. Downsample sample by 
L = 2 and lowpass filter, downsample by 3 and lowpass filter, then
downsample by L = 4 and lowpass filter. In all cases the lowpass
filter is a 10th-order Butterworth lowpass.

Parameters
----------
x : ndarray of the input signal

Returns
-------
y : ndarray of the output signal

Notes
-----
The cutoff frequency of the lowpass filters is 1/2, 1/3, and 1/4 to 
track the upsampling by 2, 3, and 4 respectively.

Examples
--------
>>> y = deci24(x)