RangedData for
wigToRangedData with chromosome and position information, sorted
in decreasing chromosal size and increasing position.
Details
Reads the entire file into memory, then processes the file in rapid fashion,
thus performance will be limited by memory capacity.
The WIG file is expected to conform to the minimal fixedStep WIG format
(see References), where each chromsome is started by a fixedStep
declaration line. The function assumes only a single track in the WIG file,
and will ignore any lines before the first line starting with fixedStep.