SQ: Stata module for sequence analysis

The term sq refers to sequence data and to the commands for analyzing these data. Sequences are entities build by a limited number of elements that are ordered in a specific way. A typical example is the human DNA, where the "Elements" Adenin, Cytosin, Guanin and Thymin (the "organic Bases") are ordered into a sequence. Other sequences are songs, that are build by tones that appear in a specific order, or careers of employers that are build by specific job-positions and ordered along time. Sequence data are data that contains one variable holding the elements, one variable that contain the position of each elements within this sequence, and one variable that identifies the sequences itself. Hence, sequence data requires data that are set up in what Stata usually calls the "long form". This version is updated from that published in Stata Journal, 2006, 6:4.