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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

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