Time axis in spectrogram for event relatd data

Question

Kim 2013-10-21

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https://ww2.mathworks.cn/matlabcentral/answers/90970-time-axis-in-spectrogram-for-event-relatd-data

评论： Kim 2013-10-22

I have EEG data that is event related so the data times actually go from -500 to 1500 ms with fs=256. I would like to create a spectrogram of the epochs with the time axis labeled correctly but just can't seem to figure it out. Any help very welcome. Thanks Kim

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Answer 1

Jeremy 2013-10-21

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Here is some lines I've used to set up a spectrogram with more control on how it is created. You should be able to use tStart to get what you need.

tStart=150; %seconds
fs=1000; %Hz
nfft=fs/binWidth; %samples
overlap = 50;%
fLimit=400; %Hz
T = 0:1/fs:2;
X = chirp(T,100,1,200,'q');
[~, f,t,P]=spectrogram(X,hann(nfft),nfft/(100/overlap),nfft,fs);
f(f>fLimit)=[];
t=t+tStart;
P=10*log10(P(1:length(f),:)');
sf=surf(f,t,P,'edgecolor','none');
view(0,90);
axis tight;