Hi Steffen I've just found a bug in GenomeGraphs. Try this code: library(GenomeGraphs) mart <- useMart("ensembl", dataset = "mmusculus_gene_ensembl") start <- 51000000 end <- 51100000 plusStrand <- makeGeneRegion( chromosome = 10, start = start, end = end, strand = "+", biomart = mart ) gdPlot( list( plusStrand ) ) I get the error > gdPlot( list( plusStrand ) ) Error in if (ens[1, 6] == 1) { : missing value where TRUE/FALSE needed The reason seems to be that the indicated interval does not contain any genes. If you set 'end' to 52000000, it works correctly. > sessionInfo() R version 2.9.0 (2009-04-17) x86_64-unknown-linux-gnu locale: LC_CTYPE=en_GB.UTF-8;LC_NUMERIC=C;LC_TIME=en_GB.UTF-8;LC_COLLATE=en_GB .UTF-8;LC_MONETARY=C;LC_MESSAGES=en_GB.UTF-8;LC_PAPER=en_GB.UTF-8;LC_N AME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_GB.UTF-8;LC_IDENTI FICATION=C attached base packages: [1] grid stats graphics grDevices utils datasets methods [8] base other attached packages: [1] GenomeGraphs_1.4.0 biomaRt_2.0.0 loaded via a namespace (and not attached): [1] RCurl_0.94-1 XML_2.3-0 Cheers Simon +--- | Dr. Simon Anders, Dipl. Phys. | European Bioinformatics Institute, Hinxton, Cambridgeshire, UK | office phone +44-1223-492680, mobile phone +44-7505-841692 | preferred (permanent) e-mail: sanders at fs.tum.de