<html><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:12pt"><div>Dear Chang</div><div>Since it is important to reduce the dimensionality of your data by adopting PCA, a simple rule is to select </div><div>an appropriate number of principal components regarding the variance of your data.</div><div><br></div><div>In MATLAB script:</div><div><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">[pc,score,latent,tsquare] = princomp( (time x triasl) x channel); % concatenate your trials in time (suggested)</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px;
padding-bottom: 0px; padding-left: 0px; ">r=find(cumsum(latent)./sum(latent) > 0.98);</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">%r(1) is the total number of components need to capture more than 98 % of the variance of </pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">%your initial data</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "><br></pre><pre class="programlisting"
style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">Afterward, proceed with the ICA.</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "><br></pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">I hope that i help you !!</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px;
padding-bottom: 0px; padding-left: 0px; "><br></pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "><br></pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "><br></pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">Best regards</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px;
padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">Stavros Dimitriadis</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; ">
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</pre><pre class="programlisting" style="margin-top: 1ex; margin-bottom: 0.7ex; margin-left: 32px; font-family: 'courier new', courier, monospace; font-size: 12px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; "><br></pre></div></div></body></html>