Hello,

as I can open an xz-compressed GFF file with read.delim but not with rtracklayer::import, I suppose that there is a but in rtracklayer…

The error message is:

Error in .normarg_input_filepath(filepath) : 
  file "test.gff3.xz" has unsupported type: xzfile

The session below look longish but I just:

• import a GFF file
• import a gz-compressed GFF file
• fail to import an xz-compressed GFF file
• read the xz-compressed GFF file as a data.frame with read.delim

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> library('rtracklayer')
Loading required package: GenomicRanges
Loading required package: stats4
Loading required package: BiocGenerics

Attaching package: ‘BiocGenerics’

The following objects are masked from ‘package:stats’:

    IQR, mad, sd, var, xtabs

The following objects are masked from ‘package:base’:

    anyDuplicated, append, as.data.frame, basename, cbind, colnames,
    dirname, do.call, duplicated, eval, evalq, Filter, Find, get, grep,
    grepl, intersect, is.unsorted, lapply, Map, mapply, match, mget,
    order, paste, pmax, pmax.int, pmin, pmin.int, Position, rank,
    rbind, Reduce, rownames, sapply, setdiff, sort, table, tapply,
    union, unique, unsplit, which.max, which.min

Loading required package: S4Vectors

Attaching package: ‘S4Vectors’

The following objects are masked from ‘package:base’:

    expand.grid, I, unname

Loading required package: IRanges
Loading required package: GenomeInfoDb
> import('test.gff3')
GRanges object with 1 range and 6 metadata columns:
      seqnames    ranges strand |   source     type     score     phase
         <Rle> <IRanges>  <Rle> | <factor> <factor> <numeric> <integer>
  [1]   ctg123 1000-9000      + |       NA     gene        NA      <NA>
               ID        Name
      <character> <character>
  [1]   gene00001        EDEN
  -------
  seqinfo: 1 sequence from an unspecified genome; no seqlengths
> import('test.gff3.gz')
GRanges object with 1 range and 6 metadata columns:
      seqnames    ranges strand |   source     type     score     phase
         <Rle> <IRanges>  <Rle> | <factor> <factor> <numeric> <integer>
  [1]   ctg123 1000-9000      + |       NA     gene        NA      <NA>
               ID        Name
      <character> <character>
  [1]   gene00001        EDEN
  -------
  seqinfo: 1 sequence from an unspecified genome; no seqlengths
> import('test.gff3.xz')
Error in .normarg_input_filepath(filepath) : 
  file "test.gff3.xz" has unsupported type: xzfile
> read.delim('test.gff3.xz', comment.char='#')
[1] ctg123                 .                      gene                  
[4] X1000                  X9000                  ..1                   
[7] X.                     ..2                    ID.gene00001.Name.EDEN
<0 rows> (or 0-length row.names)
> sessionInfo()
R version 4.1.1 (2021-08-10)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 11 (bullseye)

Matrix products: default
BLAS:   /usr/lib/x86_64-linux-gnu/blas/libblas.so.3.9.0
LAPACK: /usr/lib/x86_64-linux-gnu/lapack/liblapack.so.3.9.0

locale:
 [1] LC_CTYPE=en_GB.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_GB.UTF-8        LC_COLLATE=en_GB.UTF-8    
 [5] LC_MONETARY=en_GB.UTF-8    LC_MESSAGES=en_GB.UTF-8   
 [7] LC_PAPER=en_GB.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_GB.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] stats4    stats     graphics  grDevices utils     datasets  methods  
[8] base     

other attached packages:
[1] rtracklayer_1.53.1   GenomicRanges_1.45.0 GenomeInfoDb_1.29.5 
[4] IRanges_2.27.2       S4Vectors_0.31.3     BiocGenerics_0.39.2 

loaded via a namespace (and not attached):
 [1] rstudioapi_0.13             XVector_0.33.0             
 [3] zlibbioc_1.39.0             GenomicAlignments_1.29.0   
 [5] BiocParallel_1.27.4         lattice_0.20-44            
 [7] rjson_0.2.20                tools_4.1.1                
 [9] grid_4.1.1                  SummarizedExperiment_1.23.4
[11] parallel_4.1.1              Biobase_2.53.0             
[13] matrixStats_0.60.1          yaml_2.2.1                 
[15] crayon_1.4.1                BiocIO_1.3.0               
[17] Matrix_1.3-3                GenomeInfoDbData_1.2.6     
[19] restfulr_0.0.13             bitops_1.0-7               
[21] RCurl_1.98-1.4              DelayedArray_0.19.2        
[23] compiler_4.1.1              MatrixGenerics_1.5.4       
[25] Biostrings_2.61.2           Rsamtools_2.9.1            
[27] XML_3.99-0.7