I would deal with the datafile as a database and use SQL and its aggregate functions to condense that 9th field into a list of unique numbers with the count of them Then it becomes trivially easy to answer your question.
CountZero
A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James
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Imperial Deltronics
