I expect that the output is a p-value, correct? so the p-value will obviously only be positive. you could possibly do a couple things to retain the signs. A) you could find the indices of all negative values, and then after the signrank test multiply all of those indices by -1, or B) output separate maps for positive and negative values.<br>

<br>Cheers,<br>Michael<br><br><div class="gmail_quote">On Thu, May 19, 2011 at 11:29 AM, Jennifer Barredo <span dir="ltr">&lt;<a href="mailto:[log in to unmask]"><a href="/cgi-bin/wa-jisc.exe?LOGON=A3%3Dind1105%26L%3DSPM%26E%3Dquoted-printable%26P%3D4386483%26B%3D--20cf3040ea429b5f7d04a3a750e8%26T%3Dtext%252Fhtml%3B%2520charset%3DUTF-8%26pending%3D" target="_parent" >[log in to unmask]</a></a>&gt;</span> wrote:<br>

<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi,<br>
<br>
I&#39;ve been trying to generate a SPM for a signrank test rather than a t-test. I&#39;ve been able to get the signrank map written (using Matlab&#39;s Statistics Toolbox &amp; spm_write_vol), but in the process it seems like it&#39;s converting negative values to positive ones. Is there a default in the spm_write_vol that causes this to happen?<br>


<br>
Thanks,<br>
<font color="#888888">Jennifer<br>
</font></blockquote></div><br><br clear="all"><br>-- <br>Research Associate<br>Gazzaley Lab<br>Department of Neurology<br>University of California, San Francisco<br>