I'm using sequence analysis. I have a question about how to deal with missing data within the observation window.

The starting point of the analysis is when respondents leave secondary school (t0). I want to examine respondents' life course over a time-span of 36 months after leaving school. The dataset contains longitudinal information of respondents toward their educational histories. I arranged the data in the 'states-sequence' (STS) format. So in each month the dataset provides information on respondents' status (for example "employed" or "training").

For 58% of the sample, the data provides information over the whole observation window. So for this group, I can tell in every single month what they are doing. The sequences of the rest of the sample are shorter. Thus, the length of the sequences is not the same for all respondents.

How do I handle sequences of respondents that end before month 36? What would be the way the missing values should be handled in TraMineR?