Dear Gviz users/developers,

The package is throwing an error when I try to highlight certain regions in
the axis. The error is easily replicable:

> plotTracks(GenomeAxisTrack(range = IRanges(start = 25000, end = 25100)),
from = 1, to = 50000)

No problem with that. You get your genome axis from 1 to 50,000, and a
highlighted small region around the middle.

The error is thrown when the highlighted small region is close to the
borders:

Towards the left border:
> plotTracks(GenomeAxisTrack(range = IRanges(start = 1, end = 100)), from =
1, to = 50000)
Error in validObject(x) :
  invalid class “IRanges” object: 'widths(x)' cannot contain negative values
> plotTracks(GenomeAxisTrack(range = IRanges(start = 101, end = 200)), from
= 1, to = 50000)
Error in validObject(x) :
  invalid class “IRanges” object: 'widths(x)' cannot contain negative values

Towards the right border:
> plotTracks(GenomeAxisTrack(range = IRanges(start = 49901, end = 50000)),
from = 1, to = 50000)
Error in validObject(x) :
  invalid class “IRanges” object: 'widths(x)' cannot contain negative values
> plotTracks(GenomeAxisTrack(range = IRanges(start = 49801, end = 49900)),
from = 1, to = 50000)
Error in validObject(x) :
  invalid class “IRanges” object: 'widths(x)' cannot contain negative values

However, there's a moment when the highlighted region gets away enough from
the border that the error is avoided:

> plotTracks(GenomeAxisTrack(range = IRanges(start = 501, end = 600)), from
= 1, to = 50000)
> plotTracks(GenomeAxisTrack(range = IRanges(start = 49401, end = 49500)),
from = 1, to = 50000)

Those two run like a breeze.

Interestingly, one can also avoid the error by making the highlighted range
wider:

> plotTracks(GenomeAxisTrack(range = IRanges(start = 1, end = 1000)), from
= 1, to = 50000)
> plotTracks(GenomeAxisTrack(range = IRanges(start = 49001, end = 50000)),
from = 1, to = 50000)

Not a problem with those.

Ideas?

Thanks a lot,

Alvaro J. Gonzalez, PhD
Computational Biology
Memorial Sloan-Kettering Cancer Center
New York, NY

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