ah! That is possible, depending on your input fasta. The fasta headers need to be in a certain format (the format like in sequences from genbank). Can you show how the first headers look like in your fasta?
My fasta file looks like this: >NC_028405.1_COX1:
I managed to solve this problem!Thanks for the help.
But now I have another doubt, cause I finally managed to get the database that I want, but I got a different result and worst than when I used all NT. When I use a 'pre-made' database, shouldn't the results be better and more precise?
Thanks for the help again.
When I use a 'pre-made' database, shouldn't the results be better and
more precise?
In what way?
BLAST results are very dependent on search space (database size). This is vastly different between nt and any custom database you make so the results will be different (if you are looking at e values and such).
Can you show what your input fasta headers look like?
grep "^>" input.fasta | head -5
.