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  • Count hits in Local Blast (Blast+)

    Hi there,

    I have just run a standard Local Blast using Blast+:
    blastx -db mydb -query mysample -evalue 0.00001 -out blastxresult

    and I wonder: How to check the number of blast hits? The number of 'significant' cites in the output file is the number of hits?


    I alternative tried other approaches such as get a tabular or a xml format:
    blastx -db mydb -query mysample -evalue 0.00001 -outfmt 6 -out tab_blastxresult
    The number of rows is the number of hits?

    blastx -db mydb -query mysample -evalue 0.00001 -outfmt 5 -max_target_seqs 10 -out xml_blastxresult
    No idea about count hits in this format.


    Any help will be appreciated,

  • #2
    Number of rows that refer to your query sequence will be the "significant" (this definition depends on options you select for blast e.g. e value cutoff) hits for that query in tabular format. Are you just interested in the count (and not the actual hits)?

    Comment


    • #3
      Note that you can get multiple rows from the same match in the tabular output if multiple HSPs are given (e.g. if the target sequence contains a repeat, you could get two pairwise alignments which give HSPs passing the e-value threshold).

      You might want to look at parsing the BLAST output using BioPerl, Biopython, etc if you need to do anything more complicated with your analysis.

      Comment

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