Table of Contents

filter - digitally filter ERP data files

**filter** *filtertype*
*infile* *outfile* *cutoff* [*cutoff*]

**filter** digitally filters ERP
averaged files with either a lowpass, highpass, or bandpass filter. **filter**
uses a fast fourier transform (fft) algorithm to represent the data in
the frequency domain, applies an implementation of a 3rd order Butterworth
filter to the data, and finally converts the data back to the time domain
using an inverse fft.
*filtertype* can be one of "lp", "hp", or "bp", for
lowpass, highpass, and bandpass respectively. *infile* is the name of the
data file to be filtered. *outfile* is the name of the file to be created
which will contain the filtered data. *cutoff* is the cutoff frequency for
the filter. Note that for a bandpass filter, both a lowpass and high pass
cutoff frequency must be specified.

Ronald Ohst

**Table of Contents**