# SOLVED/ beginner level question/ how to interpret Weka generalized sequential patterns output?

Hi!

My example data (product purchase sequence):

 I II III IV V customer1 a a b e d customer2 a b e a d customer3 b e a a d customer4 c a b a a customer5 c d c a a

And Weka GSP output:

GeneralizedSequentialPatterns
=============================

Number of cycles performed: 3
Total number of frequent sequences: 9

Frequent Sequences Details (filtered):

- 1-sequences

 <{a}> (2)
 <{b}> (2)
 <{a}> (3)
 <{d}> (2)

- 2-sequences

 <{a}{a}> (2)
 <{a,b}> (2)
 <{b}{a}> (2)
 <{a,d}> (2)

- 3-sequences

 <{a,b}{a}> (2)

Question:

Does "{a,b}{a}> (2)" mean that sequence {a,b}{a} appears two times in data?
- if so, why is sequence {a,a}  not shown? It appers four times in data.

Thank you!

Markus

Hello Markus,

But to answer your question, {a,a} is shown in the result. The result is grouped by the size of the pattern. {a,a} has size 2, so it appears in the section: 2-sequence;). And gps only found one frequent  3-sequence namely <{a,b}{a}>.

Another question is, is the input table complete and correct? usually {a, b} is used for an item set in your case  one order. But if I look at your example every order contains only one item... So actually the result you got does not fit the table.

I hope i could help ;)

Greets, Sebastian

Thank you. I did not undestand the item/ item set distiction. This clarified the output.

Markus