[BioC] ggbio: mirrored coverage plots for +/- strands

[Thomas Girke]

Dear ggbio experts,

ggbio is an excellent package. Thanks for providing it. - One thing I
have not been able to figure out though is how to create mirrored
(~lacking better term here~) representations of coverage data. It is not
hard to achieve this with ggplot2, but a ggbio solution would be much
more elegant and efficient. Here is an example illustrating what I mean:

## Plotting coverage with ggbio using faceting for +/-
library(GenomicRanges); library(ggbio)
set.seed(1); N <- 100; 
gr <- GRanges(seqnames = sample(c("chr1", "chr2", "chr3"), size = N,
	replace = TRUE), IRanges(start = sample(1:300, size = N, replace =
	TRUE), width = sample(70:75, size = N,replace = TRUE)), strand =
	sample(c("+", "-"), size = N, replace = TRUE), value = rnorm(N, 10, 3),
	score = rnorm(N, 100, 30), sample = sample(c("Normal", "Tumor"), size =
	N, replace = TRUE), pair = sample(letters, size = N, replace = TRUE))
autoplot(gr, aes(color = strand, fill = strand), facets = strand ~ seqnames, stat = "coverage")

## What if I want the following mirrored layout for +/- instead:
pos <- sapply(coverage(gr[strand(gr)=="+"]), as.numeric)
pos <- data.frame(Chr=rep(names(pos), sapply(pos, length)), Strand=rep("+", length(unlist(pos))), Position=1:length(unlist(pos)), Coverage=as.numeric(unlist(pos)))
neg <- sapply(coverage(gr[strand(gr)=="-"]), as.numeric)
neg <- data.frame(Chr=rep(names(neg), sapply(neg, length)), Strand=rep("-", length(unlist(neg))), Position=1:length(unlist(neg)), Coverage=-as.numeric(unlist(neg)))
covdf <- rbind(pos, neg)
p <- ggplot(covdf, aes(Position, Coverage, fill=Strand)) +
            geom_bar(stat="identity", position="identity") + facet_wrap(~Chr)
p

Is there a way achieving the latter with ggbio directly? Most biologists would
prefer this mirrored over the faceted +/- representation. If this is already
possible then perhaps this could be added to the ggbio documentation?

Thanks, 

Thomas


> sessionInfo()
R version 3.0.2 (2013-09-25)
Platform: x86_64-apple-darwin10.8.0 (64-bit)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] parallel  stats     graphics  grDevices utils     datasets  methods
[8] base

other attached packages:
[1] ggbio_1.10.10        ggplot2_0.9.3.1      GenomicRanges_1.14.3
[4] XVector_0.2.0        IRanges_1.20.6       BiocGenerics_0.8.0

loaded via a namespace (and not attached):
 [1] AnnotationDbi_1.24.0    Biobase_2.22.0          biomaRt_2.18.0
 [4] Biostrings_2.30.1       biovizBase_1.10.5       bitops_1.0-6
 [7] BSgenome_1.30.0         cluster_1.14.4          colorspace_1.2-4
[10] DBI_0.2-7               dichromat_2.0-0         digest_0.6.3
[13] Formula_1.1-1           GenomicFeatures_1.14.2  grid_3.0.2
[16] gridExtra_0.9.1         gtable_0.1.2            Hmisc_3.13-0
[19] labeling_0.2            lattice_0.20-24         MASS_7.3-29
[22] munsell_0.4.2           plyr_1.8                proto_0.3-10
[25] RColorBrewer_1.0-5      RCurl_1.95-4.1          reshape2_1.2.2
[28] Rsamtools_1.14.2        RSQLite_0.11.4          rtracklayer_1.22.0
[31] scales_0.2.3            splines_3.0.2           stats4_3.0.2
[34] stringr_0.6.2           survival_2.37-4         tools_3.0.2
[37] VariantAnnotation_1.8.7 XML_3.95-0.2            zlibbioc_1.8.0