<div dir="ltr"><div class="markdown-here-wrapper" style=""><p style="margin:0px 0px 1.2em!important">Hi Nicola,</p>
<p style="margin:0px 0px 1.2em!important">could you post an example of the differences?<br>Also - you are probably doing something else than the code you pasted because here:</p>
<pre style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;font-size:1em;line-height:1.2em;margin:1.2em 0px"><code class="hljs language-matlab" style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248);white-space:pre;overflow:auto;border-radius:3px;border:1px solid rgb(204,204,204);padding:0.5em 0.7em;display:block!important;display:block;overflow-x:auto;padding:0.5em;color:rgb(51,51,51);background:rgb(248,248,248)">ERP1 = mean(<span class="hljs-transposed_variable">EEG.</span>data,<span class="hljs-number" style="color:rgb(0,128,128)">3</span>);
ERP2 = mean(<span class="hljs-transposed_variable">EEG.</span>data,<span class="hljs-number" style="color:rgb(0,128,128)">3</span>);
Difference_ERP = ERP1 – ERP2 ;
</code></pre>
<p style="margin:0px 0px 1.2em!important"><code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">ERP1</code> and <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">ERP2</code> are the same.</p>
<p style="margin:0px 0px 1.2em!important"><code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">pop_comperp</code> may be doing additional filtering (but if I remember correctly it should only do so if asked).</p>
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aWYgYXNrZWQpLjwvc3Bhbj48YnI+PC9wPjwvZGl2Pg==" style="height:0;width:0;max-height:0;max-width:0;overflow:hidden;font-size:0em;padding:0;margin:0">​</div></div></div><div class="gmail_extra"><br><div class="gmail_quote">2016-07-01 13:54 GMT+02:00  <span dir="ltr"><<a href="mailto:n.johnstone@surrey.ac.uk" target="_blank">n.johnstone@surrey.ac.uk</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">





<div lang="EN-GB" link="blue" vlink="purple">
<div>
<p class="MsoNormal">Dear list, <u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal" style="text-autospace:none">When calculating difference waves, I have found that when using pop_comperp the graph output differs from when I perform a subtraction in Matlab:<u></u><u></u></p>
<p class="MsoNormal" style="text-autospace:none">ERP1 = <span style="color:black">
mean(EEG.data,3); <u></u><u></u></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="color:black">ERP2 = mean(EEG.data,3);</span><u></u><u></u></p>
<p class="MsoNormal">Difference_ERP = ERP1 – ERP2 ; <u></u><u></u></p>
<p class="MsoNormal">And plot this in a Matlab figure.  <u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">The values are always larger in the Matlab figure, and look less like the difference ERP I’d expect, whereas the result of pop_comperp looks much more reasonable, as are the values. I’ve examined the pop_comperp function and it seems to
 apply the same subtraction processes as the Matlab command line subtraction – so I cannot figure out why there’d be a disparity in results.
<u></u><u></u></p>
<p class="MsoNormal">I’d like to be able to extract data from these difference waves using Matlab for statistical analyses, but I’d like to understand why these results diverge in the first instance.
<u></u><u></u></p>
<p class="MsoNormal">Can anyone offer an explanation for why there’s a ‘difference’ in my difference waves?
<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Best, <u></u><u></u></p>
<p class="MsoNormal">Nicola<u></u><u></u></p>
<p class="MsoNormal"><u></u><u></u></p>
</div>
</div>

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