title: Variable indel costs for sequences of unequal length
body: <p>I am doing Sequence Analysis in TraMineR using the Optimal Matching algorithm. Unfortunately, my <strong>sequences are of unequal length due to right-censored data</strong>. The minimum length of my sequences is 5, the maximum length 11. The variations in length are not meaningful for the dissimilarities between sequences that I am interested in. Therefore, I want to hold the influence of unequal length on the overall dissimilarities between sequences as small as possible.</p>
  
  <p>I read a possible solution to this problem in Stovel and Bolan (2004 (1)), who use <strong>variable indel costs</strong> depending on whether or not the sequences are of equal length. So, for sequences of equal length they use fixed indel costs, and for unequal length they use a reduced cost, which is "roughly one-fourth of the fixed cost”.</p>
  
  <p><strong>My questions would be:</strong> 
  In general, how should the missings be coded in TraMineR? As void elements or should I include a missing state into the alphabet? 
  Is there an option in TraMineR to apply variable indel costs, as introduced by Stovel and Bolan? If yes, how can this be done?</p>
  
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  <p>(1) Stovel, Katherine and Marc Bolan. 2004. "Residential Trajectories: Using Optimal Alignment to Reveal the Structure of Residential Mobility." Sociological Methods &amp; Research 32(4):559-598.</p>