Dear all,

I have a data.frame that looks like this.

bed <- data.frame(chrom=c(rep("Chr1",5)),
                        chromStart=c(18915152,24199229,73730,81430,89350),
                        chromEnd=c(18915034,24199347,74684,81550,89768), 
                         strand=c("-","+","+","+","+"))

write.table(bed, "test_xRNA.bed",row.names = F,col.names = F, sep="\t", quote=FALSE)

^{Created on 2022-07-29 by the [reprex package](https://reprex.tidyverse.org) (v2.0.1)}

and I want to convert it into a bed file. I try to do it with the writing.table function, but I fail miserably by taking this error comment when I look at the intersect

Error: unable to open file or unable to determine types for file test_xRNA.bed

- Please ensure that your file is TAB delimited (e.g., cat -t FILE).
- Also ensure that your file has integer chromosome coordinates in the 
  expected columns (e.g., cols 2 and 3 for BED).

Any ideas of how I can properly convert a data.frame to a .bed file in R?

I have heard about the rtracklayer package, does anyone have an experience with it?

> bed <- data.frame(chrom=c(rep("Chr1",5)),
                        chromStart=c(18915152,24199229,73730,81430,89350),
                        chromEnd=c(18915034,24199347,74684,81550,89768), 
                         strand=c("-","+","+","+","+"))

## fix mis-ordered rows
> for(i in seq_len(nrow(bed))) if(bed[i,"strand"] == "-") bed[i,2:3] <- bed[i,3:2]
> bed
  chrom chromStart chromEnd strand
1  Chr1   18915034 18915152      -
2  Chr1   24199229 24199347      +
3  Chr1      73730    74684      +
4  Chr1      81430    81550      +
5  Chr1      89350    89768      +
> bedgr <- GRanges(bed[,1], IRanges(bed[,2], bed[,3]), bed$strand)
> bedgr
GRanges object with 5 ranges and 0 metadata columns:
      seqnames            ranges strand
         <Rle>         <IRanges>  <Rle>
  [1]     Chr1 18915034-18915152      -
  [2]     Chr1 24199229-24199347      +
  [3]     Chr1       73730-74684      +
  [4]     Chr1       81430-81550      +
  [5]     Chr1       89350-89768      +
  -------
  seqinfo: 1 sequence from an unspecified genome; no seqlengths
> export(bedgr, "tmp.bed", "bed")
> import("tmp.bed")
GRanges object with 5 ranges and 2 metadata columns:
      seqnames            ranges strand |        name     score
         <Rle>         <IRanges>  <Rle> | <character> <numeric>
  [1]     Chr1 18915034-18915152      - |        <NA>         0
  [2]     Chr1 24199229-24199347      + |        <NA>         0
  [3]     Chr1       73730-74684      + |        <NA>         0
  [4]     Chr1       81430-81550      + |        <NA>         0
  [5]     Chr1       89350-89768      + |        <NA>         0
  -------
  seqinfo: 1 sequence from an unspecified genome; no seqlengths

But normally a bed file has a meaningful score, and yours is just the postions.