title: Likert grouping with different levels in R
body: <p>I would like to use the Likert package and also to group by variable and plot the result. The problem is that I have different  levels in the variabels I want to visualise. Is there a way around this ?</p>
  
  <p>A simple example to illustrate my problem:</p>
  
  <pre><code>library(reshape)
  library(likert)
  
  foo &lt;- data.frame(car = rep(c("Toyota", "BMW", "Ford"), times = 10),
                    satisfaction = c(1,3,4,7,7,6,2,3,5,5,5,2,4,1,7),
                    quality = c(1,1,3,5,4,3,6,4,3,6,6,1,7,2,7),
                    loyalty = c(1,1,3,5,4,3,9,4,3,10,6,1,7,2,8) )
  
  foo[1:4] &lt;- lapply(foo[1:4], as.factor)
  
  likt &lt;- likert(foo[,c(2:4)], grouping = foo$car)
  plot(likt)
  </code></pre>
  
  <p>error message:</p>
  
  <pre><code>Error in likert(foo[, c(2:4)], grouping = foo$car) : 
    All items (columns) must have the same number of levels
  </code></pre>