The bedGraph format allows display of continuous-valued data in track format. This display type is
useful for probability scores and transcriptome data. This track type is similar to the wiggle
(WIG) format, but unlike the wiggle format, data exported in the bedGraph format are preserved in
their original state. This can be seen on export using the table browser. For more details on data
compression in wiggle tracks see the notes section of the wiggle track description page. If you have a very large data set and you would like to
-keep it on your own server, you should use the bigWig data format.
+keep it on your own server, you should use the bigWig data format. In fact,
+an attempt to load a bedGraph custom track over 50,000,000 lines will result in an error message,
+but can be addressed by turning the bedGraph into a bigWig (see Example 3).
Note that bedGraph files cannot easily be converted to wiggle files; converting bedGraph to bigWig
and using bigWigToWig will return the original bedGraph file.
The bedGraph format is line-oriented. BedGraph data are preceded by a track definition line, which adds a number of options for controlling the default display of this track.
Following the track definition line are the track data in four column BED format:
chromA chromStartA chromEndA dataValueA
chromB chromStartB chromEndB dataValueB