[BioC] VariantAnnotation: Specifying 'seqinfo' at import with 'readVcf'

Julian Gehring julian.gehring at embl.de
Sun Nov 3 15:55:29 CET 2013

Hi Valerie and Herve,

When providing a 'Seqinfo' object as the 'genome' argument to 'readVcf', 
would it be possible to not have the requirement of the VCF header and 
the seqinfo object to have the same ordering?  As the moment 
(VariantAnnotation_1.8.2), the import will fail if this is not the case. 
  However, this requires the user to know the ordering of the seqnames 
in the VCF file beforehand.  In the ideal case, the readVcf function 
could reorder the seqnames in the way as provided by the 'genome' argument.

Best wishes

On 09/28/2013 12:57 AM, Hervé Pagès wrote:
> Hi Julian,
> With the latest devel version of GenomicRanges (1.13.48, should become
> available via biocLite() in the next 24 hours or so), setting the
> seqinfo of a big VCF object should be much faster but your mileage
> may vary. Let us know if you still find it slow enough to justify a
> mechanism for letting the user specify the seqinfo upfront when using
> readVcf() (e.g. the 'genome' arg could be renamed 'seqinfo' and accept
> everything it supports now plus a Seqinfo object).
> Cheers,
> H.
> On 09/24/2013 10:00 AM, Julian Gehring wrote:
>> Hi Valerie,
>>> Thanks for clarifying. No, there is not currently a way to do this.
>>> The 'seqinfo' on the rowData(vcf) should not be difficult to change. Can
>>> you provide more detail as to (1) why you are changing it (did readVcf()
>>> import something incorrectly or ?) and (2) what operations on the
>>> 'seqinfo' are taking a long time.
>> 'readVcf' did everything in a correct way.  I needed to add the
>> information about the genome, circularity, and seqlengths based on
>> external annotitation, since it is not part of the VCF file.
>> I can't tell you at the moment where 'seqinfo <-' spends most of its
>> time.  I'll profile it and get back to you.
>> Thank your for your quick answer and your help!
>> Best wishes
>> Julian
>>> Thanks.
>>> Valerie
>>>> Best wishes
>>>> Julian
>>>> On 09/24/2013 06:31 PM, Valerie Obenchain wrote:
>>>>> Hi Julian,
>>>>> On 09/24/2013 02:29 AM, Julian Gehring wrote:
>>>>>> Hi,
>>>>>> Is there a direct way to specifiy the 'seqinfo' of a genome for the
>>>>>> import of a VCF file using 'readVcf'?
>>>>> I think the question is how to read in a subset of
>>>>> chromosomes/positions
>>>>> from a vcf file without an accompanying tabix index. You can't.
>>>>> readVcf() requires an index when subsets are defined by
>>>>> chromosome/position. However you can read in subsets defined by INFO
>>>>> and/or GENO fields without an index.
>>>>> Approaches:
>>>>> (1) create index with ?indexTabix and specify 'which' in ScanVcfParam
>>>>> (2) use ?filterVcf to write out a new file of records of interest
>>>>>> I'm aware that one can change it
>>>>>> with the 'seqinfo' method afterwards, but for large VCF files this
>>>>>> can
>>>>>> take a significant amount of time.
>>>>> What operation is taking along time? Subsetting the VCF object by
>>>>> chromosome?
>>>>> Valerie
>>>>>> An alternative would be to sneak it in by the 'which' arguments, such
>>>>>> as:
>>>>>> readVcf(file, genome, ScanVcfParam(which = as(seq_info, "GRanges")))
>>>>>> but this requires the file to be indexed beforehand.
>>>>>> Best wishes
>>>>>> Julian
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