带IRanges的负值

Question

我使用的是生物导体的Gviz库，我试图绘制从左到右的表意图，但是我们的数据有一些负宽度，表明这幅图应该是从右到左。如何使用IRanges输入宽度负值？

下面是我们正在使用的代码：

library(Gviz)
library(IRanges)
gen <- "mm9"
chr <- "chr1"

itrack <- IdeogramTrack(genome = gen, chromosome = chr)
gtrack <- GenomeAxisTrack()

dat <- read.delim("C:/R/mydata.TXT", header = FALSE, sep ="\t")
s <- dat[[2]]
e <- dat[[3]]
l <- dat[[4]]

annot1 = IRanges(start = s, width = l)
Error.Call2("solve_user_SEW0", start, end, width, PACKAGE = "IRanges") : 
solving row 1: negative widths are not allowed

# Those logical following commands work well if no negative integer is passed to IRanges
atrack <- AnnotationTrack (annot1, chromosome = chr, genome = gen, name = "foo") 
plotTracks (list(itrack, gtrack, atrack))

(谢谢：)

Answer 1

就像错误信息说的，IRanges不可能有负宽度--“开始”总是最左边的。可能在GRanges对象中使用strand="-"