title: How to configure x-axis using seqplot in R?
body: <p>Following up on another <a href="https://stackoverflow.com/questions/18187308/how-to-configure-y-axis-using-seqiplot-in-r">question concerning the y-axis of sequence plots</a>, I am looking for a way to manipulate the x-axis of a sequence plot using the R-package <code>TraMineR</code>. </p>
  
  <p>The problem is that <code>TraMineR</code> ships with an easy way to adjust the x-axis specifying <code>xtstep=</code>. However, this gives no full control over the x-axis as it is not possible to specify the number of ticks, tick labels and the end/limit of the scale independent of each other. In some cases, this might be a nice feature, as you can see using this example code or conferring to the two images below:</p>
  
  <pre><code>library(TraMineR) 
  data(mvad)
  mvad.alphabet &lt;- c("employment", "FE", "HE", "joblessness", "school",
                     "training")
  mvad.labels &lt;- c("Employment", "Further Education", "Higher Education",
                   "Joblessness", "School", "Training")
  mvad.scodes &lt;- c("EM", "FE", "HE", "JL", "SC", "TR")
  
  ## Define sequence objects
  mvad.seq &lt;- seqdef(mvad[, 17:86], alphabet = mvad.alphabet,
                     states = mvad.scodes, labels = mvad.labels, weights = mvad$weight)
  
  ## Plots
  seqIplot(mvad.seq, border=NA, xtstep=1, sortv="from.start") # Many ticks, some tick labels, x-scale shows last month as tick 
  seqIplot(mvad.seq, border=NA, xtstep=12, sortv="from.start") # Few ticks, few tick labels, x-scale ends before last 8 months
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/cZBr6.png" alt="Sequence plot using xtstep=1">
  Sequence index plot using xtstep=1</p>
  
  <p><img src="https://i.stack.imgur.com/n1kY5.png" alt="Sequence plot using xtstep=12">
  Sequence index plot using xtstep=12</p>