| SPECTOPO | Plot the mean log spectrum of a set of data epochs at all channels as a bundle of traces. At specified frequencies, plot the relative topographic distribution of power. Uses Matlab psd() from signal processing toolbox. |
| Usage: | >> [spectra,freqs] = spectopo(data,frames,srate,freqs,chanlocs, limits,title,freqfaq, percent, 'key1', 'value1' ...); |
| Inputs: | |
data |
(nchans,frames*epochs); % can be single-epoch |
frames |
frames per epoch {0 -> whole data length} |
srate |
sampling rate per channel (Hz) |
freqs |
vector of frequencies for topoplot scalp maps (Hz) |
chanlocs |
electrode locations file (format: >> topoplot example) |
| Optional inputs: | |
limits |
axis limits [xmin xmax ymin ymax cmin cmax] To use data limtis, omit final values or use nan's i.e. [-100 900 nan nan -10 10], [-100 900] Note that default color limits are symmetric around 0 and are different for each head {defaults: all nans} |
title |
quoted plot title {default: none} |
freqfac |
int power of 2 => approximate frequencies/Hz {default: 4} |
percent |
downsampling factor or approximate percentage of the data to keep while computing spectra. Downsampling can help to speed up the computation. From 0 to 1 {default: 1} |
'key','val' |
optional topoplot arguments (see topoplot) |
| Outputs: | |
spectra |
(nchans,nfreqs) power spectra (average over epochs) in dB |
freqs |
frequencies of spectra (Hz) |
| Authors: | Scott Makeig & Marissa Westerfield, SCCN/INC/UCSD, La Jolla, 3/01 |
| See also: | timtopo, envtopo, tftopo, topoplot |