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<p class="MsoNormal">Hi Mike & others,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Instead of specifying a set number of components (e.g. 51) I tend to use data-driven approach that reduces my data to the number of components that describes 99% of the variance in my covar matrix. I do this like so:<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">covar = zeros(numel(data.label));</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:blue">for</span><span style="font-size:10.0pt;font-family:"Courier New";color:black"> itrial = 1:numel(data.trial)</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> currtrial = data.trial{itrial};</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black"> covar = covar + currtrial*currtrial.';</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:blue">end</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">[V, D] = eig(covar);</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">D = sort(diag(D),</span><span style="font-size:10.0pt;font-family:"Courier New";color:#A020F0">'descend'</span><span style="font-size:10.0pt;font-family:"Courier New";color:black">);</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">D = D ./ sum(D);</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">Dcum = cumsum(D);</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">numcomponent = find(Dcum>.99,1,</span><span style="font-size:10.0pt;font-family:"Courier New";color:#A020F0">'first'</span><span style="font-size:10.0pt;font-family:"Courier New";color:black">)
+1; </span><span style="font-size:10.0pt;font-family:"Courier New";color:forestgreen">% number of components accounting for 99% of variance in covar matrix</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:forestgreen"></span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">disp(sprintf(</span><span style="font-size:10.0pt;font-family:"Courier New";color:#A020F0">'\n Reducing the data to %d components \n'</span><span style="font-size:10.0pt;font-family:"Courier New";color:black">,numcomponent));</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black"></span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">cfg = [];</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">cfg.method =
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#A020F0">'pca'</span><span style="font-size:10.0pt;font-family:"Courier New";color:black">;</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">cfg.updatesens =
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#A020F0">'yes'</span><span style="font-size:10.0pt;font-family:"Courier New";color:black">;</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">cfg.channel =
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#A020F0">'MEG'</span><span style="font-size:10.0pt;font-family:"Courier New";color:black">;</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">comp = ft_componentanalysis(cfg, data);</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black"></span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">cfg = [];</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">cfg.updatesens =
</span><span style="font-size:10.0pt;font-family:"Courier New";color:#A020F0">'yes'</span><span style="font-size:10.0pt;font-family:"Courier New";color:black">;</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">cfg.component = comp.label(numcomponent:end);</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:10.0pt;font-family:"Courier New";color:black">data_fix = ft_rejectcomponent(cfg, comp);</span><span style="font-size:12.0pt;font-family:"Courier New""><o:p></o:p></span></p>
<p class="MsoNormal"><o:p></o:p></p>
<p class="MsoNormal">Cheers, <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Robert Seymour (Aston Brain Centre)<o:p></o:p></p>
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