Converting a Transaction Database to a Sequence Database (SPMF documentation)
This example explains how to convert a transaction database to a sequence database using the SPMF open-source data mining library.
How to run this example?
- If you are using the graphical interface, (1) choose the "Convert_transaction_database_to_sequence_database" algorithm, (2) select the input file "contextPasquier99.txt", (3) set the output file name (e.g. "output.txt") and sequence count = 5 (5) click "Run algorithm".
- If you want to execute this example from the command line,
then execute this command:
java -jar spmf.jar run Convert_transaction_database_to_sequence_database contextPasquier99.txt output.txt 5 in a folder containing spmf.jar and the example input file contextPasquier99.txt. - If you are using the source code version of SPMF, launch the file "MainTestConvertTransDBtoSeqDB.java" in the package ca.pfv.SPMF.tests
What is this tool?
This tool converts a transaction database to a sequence database. It should be used carefully since it assumes that each transaction is a sequence, and that items in each transaction are sequentially ordered, which is usually not the case in real-life transaction databases.
What is the input?
The tool takes two prameters as input:
- an input file (the transaction database),
- the number of lines of the input file to be converted
A transaction database is a set of transactions. Each transaction is a set of items. For example, consider the following transaction database. It contains 5 transactions (t1, t2, ..., t5) and 5 items (1,2, 3, 4, 5). For example, the first transaction represents the set of items 1, 3 and 4. This database is provided as the file contextPasquier99.txt in the SPMF distribution. It is important to note that an item is not allowed to appear twice in the same transaction and that items are assumed to be sorted by lexicographical order in a transaction.
| Transaction id | Items |
| t1 | {1, 3, 4} |
| t2 | {2, 3, 5} |
| t3 | {1, 2, 3, 5} |
| t4 | {2, 5} |
| t5 | {1, 2, 3, 5} |
What is the output?
The output is a sequence database in SPMF format. A sequence database is a set of sequences. Each sequence is an ordered list of itemsets. Each itemset is an unordered set of items (symbols) represented by positive integers. The output for this example is the following sequence database. It contains five sequences. The first sequence indicates that item 1 is followed by item 3, which is followed by item 4.
| Sequence id | Itemsets |
| s1 | {1},{3}, {4} |
| s2 | {2},{3},{5} |
| s3 | {1}, {2}, {3}, {5} |
| s4 | {2}, {5}, |
| s5 | {1}, {2}, {3}, {5} |
Input file format
The input file format is defined as follows. It is a text file. An item is represented by a positive integer. A transaction is a line in the text file. In each line (transaction), items are separated by a single space. It is assumed that all items within a same transaction (line) are sorted according to a total order (e.g. ascending order) and that no item can appear twice within the same line.
For example, for the previous example, the input file is defined as follows:
1 3 4
2 3 5
1 2 3 5
2 5
1 2 3 5
Output file format
The output file format is defined as follows. It is a text file where each line represents a sequence from a sequence database. Each item from a sequence is a positive integer and items from the same itemset within a sequence are separated by single space. Note that it is assumed that items within a same itemset are sorted according to a total order and that no item can appear twice in the same itemset. The value "-1" indicates the end of an itemset. The value "-2" indicates the end of a sequence (it appears at the end of each line). For example, the output file for this example contains five lines (five sequences).
1 -1 3 -1 4 -1 -2
2 -1 3 -1 5 -1 -2
1 -1 2 -1 3 -1 5 -1 -2
2 -1 5 -1 -2
1 -1 2 -1 3 -1 5 -1 -2
The first line represents a sequence where the item 1 is followed by item 3, which is followed by item 4.