Reads a transcript list, computes the average value of some WIG data (please consult http://genome.ucsc.edu/goldenPath/help/wiggle.html to know more about this format) for each transcript and adds a tag corresponding to this average value to the transcript.
The script finds all the data which correspond to the genomic coordinates of a transcript, average these data and store the result into a tag. Then, the transcripts are written in an output file, together with the tag.
You can then plot your data using plotTranscriptList.py.