Abbreviations in Sequence Regression Trees

Question

I use Sequence Regression Trees to examine differences in career trajectories. Both in the plot as well as in the printed description of the tree, there are abbreviations that are not explained neither in the TraMineR help menu nor in Matthias Studer's paper on Sequence Regression Trees/Weighted Clusters.

Can you please let me know what the following abbreviations in the example below mean (d-plot on hierarchical advancement of 377 participants over 15 years (30 periods of 6 months each)? Thank you very much!

PRINTED OUTPUT

Dissimilarity tree:
 Parameters: minSize=18.85, maxdepth=3, R=5000, pval=0.01 
 Formula: matOM ~ Age + Degree + Gender + YearsSinceGrad 
 Global R2: 0.011589 

 Fitted tree: 

 |-- Root  (n: 377 disc: 0.55559) 
   |-> Age 0.011589 
             |-- <= 48 with NA    (n: 260 disc: 0.53812)[(1,20)-(2,8)-(3,2)] * 
             |-- > 48    (n: 117 disc: 0.57369)[(1,14)-(2,12)-(3,4)] * 

Question 1: disc = ? (--> Equals s2 in the plot, see below) Question 2: [(1,20)-(2,8)-(3,2)] * = ? (Is this the most typical sequence?)

PLOTTED OUTPUT Question 3: s2 = ? (Equals "disc" in printed output above)

Answer 1

Thank you for your remarks!

Question 1: Yes, 'disc' = 's2' in the plot (I have to fix this). This means "discrepancy". A high discrepancy means that there are a lot of variations accross the sequences. The range of the discrepancy is [0, maximum possible distance] and there is thus no threashold values. But you can compare some values.

The Levene test (which seems to be non-significant in your case, see the image) test the significativity of the difference in discrepancies. This test can be run with the dissassoc function. In the tree, the Levene test the equality of discrepancy in the terminal nodes (again, here differencies seems non significant).

Question 2: In the printed output, the sequence in square brackets [] is the centroid. This is the most central sequence of the subgroup.

Question 3: see answer to question 1.

Hope this helps.