How to group factor levels?
<p>I have a factor column with football position abbreviations, around 17 unique values with 220 observations. I want to have only three factor levels which encompass the 17 unique values.</p>

<pre><code>levels(nfldraft$Pos) &lt;- list(Linemen = c("C","OG","OT","TE","DT","DE"),
                             Small_Backs =  c("CB","WR","FS"), 
                             Big_Backs = c("FB","ILB","OLB","P","QB",
                                           "RB","SS","WR"))
</code></pre>

<p>is what I tried, printing <code>nfldraft$Pos</code> to the console shows 3 factor levels but all the values are either <code>"Linemen"</code> or <code>"Small_Backs"</code> and all the other ones are <code>NA</code>. Where am I going wrong?</p>