title: change line width in parallel coordinate plot in R
body: <p>My question is I want to change the line width of parallel coordinate according to a specific column, for example I want the record with <code>type==mean</code> become thicker than other individual lines. But it seems that <code>ggparcoord</code> does not have that option but only has the option to change the <code>alpha</code> of the line. Any idea about how to do this? maybe use <code>mapping</code> option?</p>
  
  <p>A reproducible example could be </p>
  
  <pre><code>library(dplyr)
  library(GGally)
  mean_row = select(iris,-Species) %&gt;% summarise_each(funs(mean)) %&gt;% mutate(Species="mean")
  iris2 = rbind(mean_row,iris)
  gpd &lt;- ggparcoord(data = iris2, columns = 1:4, groupColumn = 5)
  </code></pre>