I have noticed an error while using another package when it was trying to open a browser and view custom tracks in UCSC genome. I decided to just see if I could run a simple browserView() directly in a new R session and I still seem to have an error. Any idea what might be going on? Here is my code followed by an error and a traceback() > library(rtracklayer) > session <- browserSession() > browserView(session, GRangesForUCSCGenome(genome="hg19, chrom="chr2", IRanges(20000, 50000))) Warning message: In .local(object, range, track, ...) : NAs introduced by coercion Error in ucscTrackModes(ucscTracks(object)) : error in evaluating the argument 'object' in selecting a method for function 'ucscTrackModes': Error in names(trackIds) <- sub("^ ", "", sapply(nodes, xmlValue)) : attempt to set an attribute on NULL > traceback() 7: ucscTrackModes(ucscTracks(object)) 6: .local(object, ...) 5: ucscTrackModes(view) 4: ucscTrackModes(view) 3: .local(object, range, track, ...) 2: browserView(session, GRangesForUCSCGenome(genome = "hg19", chrom = "chr2", IRanges(20000, 50000))) 1: browserView(session, GRangesForUCSCGenome(genome = "hg19", chrom = "chr2", IRanges(20000, 50000))) -- output of sessionInfo(): R version 3.0.2 (2013-09-25) Platform: x86_64-unknown-linux-gnu (64-bit) locale: [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8 [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8 [7] LC_PAPER=en_US.UTF-8 LC_NAME=C [9] LC_ADDRESS=C LC_TELEPHONE=C [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C attached base packages: [1] parallel stats graphics grDevices utils datasets methods [8] base other attached packages: [1] rtracklayer_1.22.3 GenomicRanges_1.14.4 XVector_0.2.0 [4] IRanges_1.20.6 BiocGenerics_0.8.0 loaded via a namespace (and not attached): [1] Biostrings_2.30.1 bitops_1.0-6 BSgenome_1.30.0 RCurl_1.95-4.1 [5] Rsamtools_1.14.3 stats4_3.0.2 tools_3.0.2 XML_3.98-1.1 [9] zlibbioc_1.8.0 -- Sent via the guest posting facility at bioconductor.org.