[Eeglablist] Re: timef/crossf 'padratio'
smakeig at ucsd.edu
Thu Dec 9 12:37:37 PST 2004
In timef() and crossf(), the parameter 'padratio' does what it says. It
pads a tapered data window of length winsize with (padratio-1)*winsize
zeros. Delivered to an FFT, this gieves padratio times as many
frequencies - though without actually increasing the freq resolution, in
the sense that two very nearby frequencies could now be resolved. It
does allow localization of the center of a single frequency peak, and
makes prettier figures...
PS A 'padratio' of 16 is high - try 4 and 1 to compare.
PPS A more common problem is not knowing how to get low frequencies from
timef(). Using the modified wavelet option ('cycles', [3 0.5]), an
optional argument 'winsize', round(EEG.srate), applied to 3-sec epochs,
will give a low frequency of 3 Hz. This is the default we use.
naeem at sbox.tugraz.at wrote:
>I am using eeglab for data analysis.
>There is a parameter 'padratio'used in plot channel time
> I am not able to understand what this parameter does?
>In tutorial this value is set to be 16-what is the criterion for a particular
>value of this parameter?
>I will appreciate any help
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