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  • Entrez esearch.fcgi large set of sequences download: fluctuating number of sequences

    Hello everybody!

    I have a little problem: I'm trying to download a large set of fasta sequences from Entrez, but the number of sequences retrieved differs from the announced number:
    When I am using the link in a browser:
    Code:
    https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=nucleotide&term=Phaeophyceae[Organism]&usehistory=y
    It will give me a certain number of sequences.
    But when I use the perl script (as explain here: https://www.ncbi.nlm.nih.gov/books/N..._esayers-5-4-3), the number of final fasta sequences is always lower...
    I am using just a small difference compared with the tutorial:
    Code:
            $efetch_url = $base ."efetch.fcgi?db=nucleotide&WebEnv=$web";
            $efetch_url .= "&query_key=$key&retstart=$retstart";
            $efetch_url .= "&retmax=$retmax&rettype=fasta&retmode=text";
    Does anybody had the same problem before? Does anybody know where does it come from and how to fix it?

    Thanks in advance,
    Denis

  • #2
    Ok, I found the problem: DO NOT USE eUtils !

    Use Entrez Direct instead, It's really working (be sure to install the latest NCBI version and not the aptitude package)
    https://www.ncbi.nlm.nih.gov/books/NBK179288/

    Comment


    • #3
      NCBI requires use of API tokens with eUtils as May 1st, 2018. It you are running a large amount of queries some of those may fail, which may explain the variable numbers. Just a thought.
      Last edited by GenoMax; 06-21-2018, 06:26 AM.

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