Julian Gehring | 30 Sep 13:53 2013
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Re: VariantAnnotation: Specifying 'seqinfo' at import with 'readVcf'

Hi Valerie and Herve,

Your latest changes improve the speed of this greatly, thanks for your work!

Thinking more generally, do you think it would be worth generalizing the 
readVcf in the way you described?  I'm not just thinking about speed 
here, but also about a more flexible way of interacting with the 
functions (given that the user has to specify the genome name anyway).

Best wishes
Julian

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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