Entering edit mode
7.6 years ago
xi100f
•
0
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
It could be due to numerical precision, i.e. at some point 1e-180 = 0.