title: Moving from a matrix of character names to a vector of those names (for fMRI data)
body: <p>I have a lower triangular matrix of fMRI network connectivities of sum(1:235), so there are 27730 values. I have these values, however, I want to cbind another vector that has the names of these regions of interest (ROIs), but I'm not sure how I can move from the 236 vector of these ROIs to the filled out 27730 vector.</p>
  <p>So the connections should go like this: SN1-SN2, SN1-SN3…..SN1-CB4, SN2-SN3 …. SN2-CB4, SN3-SN4 …SN3-CB4 and so on. If you take all the unique connections, then the first of 236 ROIs has 235 connections, second ROI has 234 connections, third ROI has 233 connections and so on. So the total unique connections are sum(1:235) = 27730.</p>
  <p>Per a comment, though, I have changed the vector to only contain 7 of these values.</p>
  <p>Thus, I've also changed the connectivities to have sum(1:8) values.</p>
  <p>Thanks much!</p>
  <pre class="lang-r prettyprint-override"><code>roi &lt;- c(&quot;SN2&quot;, &quot;SN3&quot;, &quot;SN4&quot;, &quot;SN5&quot;, &quot;CON1&quot;, &quot;CON2&quot;, &quot;CB4&quot;)
  </code></pre>
  <pre><code>connectivities &lt;- rnorm(1:28)
  </code></pre>