Blast 2.28 evalue threshold for saving hits
Hi,
I am trying to limit number of saved hits to only those with evalues <1e-180.
According to help file of blast I use ( BLAST 2.2.28+) one of the general serch options is
-evalue <Real>
Expectation value (E) threshold for saving hits
Default = `10'
but
blastn -db blast.db -query queryfile -outfmt 6 -evalue 1e-180 > blast.out
returns only hits with evalue 0.0
while
blastn -db blast.db -query queryfile -outfmt 6 > blast.out
returns plenty of hits including those with evalues greater or lesser than 1e-180.
Does anyone knows what I am doing wrong?
Thanks in advance!
X
• 2,696 views
•
link
0 answers
No answers yet.
Log in to answer this question.
It could be due to numerical precision, i.e. at some point 1e-180 = 0.