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POFrom dataframe to vertex/edge array
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  1. POFrom dataframe to vertex/edge array
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    copied!<p>I have the dataframe</p> <pre><code>test &lt;- structure(list( y2002 = c("freshman","freshman","freshman","sophomore","sophomore","senior"), y2003 = c("freshman","junior","junior","sophomore","sophomore","senior"), y2004 = c("junior","sophomore","sophomore","senior","senior",NA), y2005 = c("senior","senior","senior",NA, NA, NA)), .Names = c("2002","2003","2004","2005"), row.names = c(c(1:6)), class = "data.frame") &gt; test 2002 2003 2004 2005 1 freshman freshman junior senior 2 freshman junior sophomore senior 3 freshman junior sophomore senior 4 sophomore sophomore senior &lt;NA&gt; 5 sophomore sophomore senior &lt;NA&gt; 6 senior senior &lt;NA&gt; &lt;NA&gt; </code></pre> <p>and I need to create a vertex/edge list (for use with igraph) with every time the student category changes in consecutive years, while ignoring when there is no change, as in</p> <pre><code>testvertices &lt;- structure(list( vertex = c("freshman","junior", "freshman","junior","sophomore","freshman", "junior","sophomore","sophomore","sophomore"), edge = c("junior","senior","junior","sophomore","senior","junior", "sophomore","senior","senior","senior"), id = c("1","1","2","2","2","3","3","3","4","5")), .Names = c("vertex","edge", "id"), row.names = c(1:10), class = "data.frame") &gt; testvertices vertex edge id 1 freshman junior 1 2 junior senior 1 3 freshman junior 2 4 junior sophomore 2 5 sophomore senior 2 6 freshman junior 3 7 junior sophomore 3 8 sophomore senior 3 9 sophomore senior 4 10 sophomore senior 5 </code></pre> <p>At this point I'm ignoring the ids, my graph should weight edges by count (i.e., freshman -> junior =3). The idea is to make a tree graph. I know it is beside the main munging point, but that's in case you ask...</p>
 

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