ir accepts FASTA formatted input data.
The program only recognizes positions occupied by one of the four characters
A, C, G, and T, which can be either in upper or lower case. Other characters
are treated as missing data. In the computation of global Ir they are
ignored. In the window analysis only windows consisting entirely of the four
canonical characters are considered. Windows containing other sequence data
are assigned an Ir value of ``n/a'' for ``not available''.
