there are undoubtedly many possibilities, here is a simple stepwise approach
using a closure to satisfy the constraint on filter form (must be
function of one argument 'x')
firstIsX = function(sro, X) {
as(substr(sread(sro),1,1),"character") == X
}
firstIsA = srFilter(function(x) firstIsX(x,"A"), name="firstIsA")
example(srFilter) # to get aln, an instance of AlignedRead, into scope
aln[firstIsA(aln)] # seems to comply
sread( aln[ firstIsA(aln) ] ) # seems to do what was requested
On Tue, Feb 9, 2010 at 3:30 PM, joseph <[email protected]> wrote:
> Hi
> can you help me create a filter to subset only reads that start with a
> particular nucleotide, for example G?
> Many thanks
> -Joseph
>
>
>
>
> [[alternative HTML version deleted]]
>
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