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    Hi Ion,<br>
    <br>
    A frequency is by definition at least a peak and a trough(up flank
    and down flank), making it one cycle (think of sinusoid here). Thus,
    you could say that one needs at least one cycle of a certain
    frequency such that it is eligible to talk about a 'frequency'. Just
    in case you don't know it already, you might want to look things up
    as Rayleigh frequency, Nyquist frequency, and I would suggest that
    you read (or start reading) the digitial signal processing book:
    <a class="moz-txt-link-freetext" href="http://www.dspguide.com/">http://www.dspguide.com/</a><br>
    <br>
    Note that a true oscillation is usually considered to last at least
    three cycles (of course, opinions differ her - I go with four). The
    length of the window of interest reflects the number of cycles that
    can be estimated. For source reconstruction, make sure cfg.toilim is
    as long as the number of cycles you want to estimate, e.g. when
    using cfg.foi = 10, then cfg.toilim(2)-cfg.toilim(1) should be at
    least 400ms when you want an estimate of 4 cycles.<br>
    <br>
    Hope it helps!<br>
    Best,<br>
    Jörn<br>
    <br>
    <br>
    <br>
    On 3/27/2012 12:46 PM, Ion Lavado wrote:
    <blockquote
cite="mid:CAMLwyK7xrbbd6_2=0MiJyXQ2OGjESnLn6TnK1R7Tqzanywk9gA@mail.gmail.com"
      type="cite">Thank you Stephan, just one thing, why i need a time
      window big enough? so i'm just studying the frequency.<br>
      <br>
      Best,<br>
      <br>
      Mikel<br>
      <br>
      <div class="gmail_quote">2012/3/27 Stephan Moratti <span
          dir="ltr"><<a moz-do-not-send="true"
            href="mailto:smoratti@psi.ucm.es">smoratti@psi.ucm.es</a>></span><br>
        <blockquote class="gmail_quote" style="margin:0pt 0pt 0pt
          0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
          <div style="word-wrap:break-word">Dear Mikel,
            <div><br>
            </div>
            <div>I understand that you should do a mtmfft with a center
              frequency of interest (in your case cfg.foil = [11 11])
              and then you do a frequency smoothing of 3 Hz
              (cfg.tapsmofrq = 3). Of course you need a time window big
              enough to allow such a smoothing. The CSD should represent
              a frequency window of 8 to 14 Hz then. Then you put the
              result of the mtmfft into the dics beamformer.</div>
            <div><br>
            </div>
            <div>Best,</div>
            <div><br>
            </div>
            <div>Stephan</div>
            <div> <br>
              <div>
                <div>El 27/03/2012, a las 11:19, Ion Lavado escribió:</div>
                <br>
                <blockquote type="cite">
                  <div>
                    <div class="h5"><span>Hello, i'm having problems
                        trying the beamformer analysis with a frequency
                        band of interest. I would like to have for
                        example an interval like [8 14] Hz. My concept
                        problem is about the cfg.frequency and
                        cfg.tapsmofrq  values. (it must be a escalar,
                        but i want a frequency band). </span>
                      <div>
                        <br>
                      </div>
                      <div>%FREQ ANALYSIS</div>
                      <div>
                        <div>cfg = [];</div>
                        <div>cfg.method    = 'mtmfft';</div>
                        <div>cfg.output    = 'powandcsd';</div>
                        <div>cfg.tapsmofrq = 5;</div>
                        <div>cfg.foilim    = [8 14];</div>
                        <div>freq_words_alpha = ft_freqanalysis(cfg,
                          words);</div>
                      </div>
                      <div><br>
                      </div>
                      <div><br>
                      </div>
                      <div>%SOURCE ANALYSIS</div>
                      <div>
                        <div>cfg              = []; </div>
                        <div>cfg.frequency    = 11;  </div>
                        <div>
                          cfg.lambda=0;</div>
                        <div>cfg.method       = 'dics';</div>
                        <div>cfg.coordsys       = 'neuromag';</div>
                        <div>cfg.projectnoise = 'yes';</div>
                        <div>cfg.grad            = 
                          freq_words_alpha.grad;</div>
                        <div>
                          cfg.channel   = {'MEG'}; </div>
                        <div>cfg.grid         = grid; </div>
                        <div>cfg.reducerank      = 2;</div>
                        <div>cfg.vol          = vol02;</div>
                        <div>vol02=ft_convert_units(vol02,'cm');</div>
                        <div>source_pre11  = ft_sourceanalysis(cfg, 
                          freq_words_alpha );</div>
                      </div>
                      <div><br>
                      </div>
                      <div><br>
                      </div>
                      <div>I use a cfg.frequency of 11 but i don't have
                        really clear what i'm doing as a get the same
                        result using cfg.frequency=11 but a freqanalysis
                        in [10 12]. I would be very grateful if someone
                        could solve my doubt.</div>
                      <div><br>
                      </div>
                      <div>Best wishes,</div>
                      <div><br>
                      </div>
                      <div>Mikel</div>
                    </div>
                  </div>
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                                <div>
                                  <br>
________________________________________________________</div>
                                <div>Stephan Moratti, PhD<br>
                                  <br>
                                </div>
                                <div>see also: <a moz-do-not-send="true"
                                    href="http://web.me.com/smoratti/"
                                    target="_blank">http://web.me.com/smoratti/</a><br>
                                  <br>
                                </div>
                                <div>
                                  Universidad Complutense de Madrid</div>
                                <div>Facultad de Psicología</div>
                                <div>Departamento de Psicología Básica I</div>
                                <div>Campus de Somosaguas</div>
                                <div>28223 Pozuelo de Alarcón (Madrid)</div>
                                <div>Spain</div>
                                <div><br>
                                </div>
                                <div>and</div>
                                <div><br>
                                </div>
                                <div>Center for Biomedical Technology</div>
                                <div>Laboratory for Cognitive and
                                  Computational Neuroscience</div>
                                <div>Parque Científico y Tecnológico de
                                  la Universidad Politecnica de Madrid<br>
                                  Campus Montegancedo</div>
                                <div>28223 Pozuelo de Alarcón (Madrid)</div>
                                <div>Spain<br>
                                  <br>
                                  <br>
                                  email: <a moz-do-not-send="true"
                                    href="mailto:smoratti@psi.ucm.es"
                                    target="_blank">smoratti@psi.ucm.es</a><br>
                                  Tel.:    <a moz-do-not-send="true"
                                    href="tel:%2B34%20679219982"
                                    value="+34679219982" target="_blank">+34
                                    679219982</a><br>
                                  <br>
                                </div>
                              </span></div>
                          </span></div>
                      </span></div>
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      <pre wrap="">_______________________________________________
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    </blockquote>
    <br>
    <br>
    <pre class="moz-signature" cols="72">-- 
Jörn M. Horschig
PhD Student
Donders Institute for Brain, Cognition and Behaviour 
Centre for Cognitive Neuroimaging
Radboud University Nijmegen 
Neuronal Oscillations Group

P.O. Box 9101
NL-6500 HB Nijmegen
The Netherlands

Contact:
E-Mail: <a class="moz-txt-link-abbreviated" href="mailto:jm.horschig@donders.ru.nl">jm.horschig@donders.ru.nl</a>
Tel:    +31-(0)24-36-68493
Web: <a class="moz-txt-link-freetext" href="http://www.ru.nl/donders">http://www.ru.nl/donders</a>

Visiting address:
Trigon, room 2.30
Kapittelweg 29
NL-6525 EN Nijmegen
The Netherlands</pre>
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