NANs in Time frequency analysis.

Jan Mathijs Schoffelen Jan.Schoffelen at FCDONDERS.RU.NL
Thu Mar 29 16:34:31 CEST 2007

Dear Sameer,

A nan is given back at those time-frequency points at which no value can be
estimated. This means that at the toi-foi pairs you specified in your
configuration, the corresponding timewindow as specified in t_ftimwin cannot
be completely filled with data. In your case, I therefore expect this
'problem' to be worse for the lower frequencies. It might seem a sorry
answer, but this is just a thing you have to live with.



-----Original Message-----
From: FieldTrip discussion list [mailto:FIELDTRIP at NIC.SURFNET.NL] On Behalf
Of Sameer Walawalkar
Sent: Thursday, March 29, 2007 4:21 PM
Subject: [FIELDTRIP] NANs in Time frequency analysis.


I am using the following settng to run time frequency analysis.

cfgTFR = [];
cfgTFR.output       = 'pow';      = 'MEG';
cfgTFR.method       = 'mtmconvol';
cfgTFR.foi          = 05 : 2 : 35;
cfgTFR.t_ftimwin    = 5./cfgTFR.foi;
cfgTFR.tapsmofrq    = 0.4 *cfgTFR.foi;
cfgTFR.toi          = 1:0.05:2.5;
cfgTFR.pad          = 'maxperlen';

TFRmult = freqanalysis(cfgTFR, data);

and find that the TFRplots for all channels (plottd using multiplot) are
always deep blue in the high time end, especially at low frequencies.

Inspection of TFR mult shows many NANs in the corresponding time regions.

Does anyone has any ideas about this?

thanks for your reply.


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