The bigWig format is for display of dense, continuous data that will be displayed in the Genome Browser as a graph. BigWig files are created initially from wiggle (wig) type files, using the program wigToBigWig. The resulting bigWig files are in an indexed binary format. The main advantage of the bigWig files is that only the portions of the files needed to display a particular region are transferred to UCSC, so for large data sets bigWig is considerably faster than regular wiggle files. The bigWig file remains on your web accessible server (http, https, or ftp), not on the UCSC server. Only the portion that is needed for the chromosomal position you are currently viewing is locally cached as a "sparse file". |
bedmap
tool. As an example, the following figure
demonstrates the speed when intersecting GENCODE exons against 1, 10,
and 100 million BAM alignments from an exome capture experiment. Whereas
in version 2.16.2 this wuld have taken 80 minutes, it now takes 80 seconds.