seqfu stats

stats is one of the core subprograms of SeqFu.

Usage: stats [options] [<inputfile> ...]

  -a, --abs-path         Print absolute paths
  -b, --basename         Print only filenames
  -n, --nice             Print nice terminal table
  -j, --json             Print json (EXPERIMENTAL)
  -s, --sort-by KEY      Sort by KEY from: filename, counts, n50, tot, avg, min, max
                         descending for values, ascending for filenames [default: none]
  -r, --reverse          Reverse sort order
  -t, --thousands        Add thousands separator (only tabbed/nice output)
  --csv                  Separate output by commas instead of tabs
  --gc                   Also print %GC
  --multiqc FILE         Saves a MultiQC report to FILE (suggested: name_mqc.txt)
  --precision INT        Number of decimal places to round to [default: 2]
  --noheader             Do not print header
  -v, --verbose          Verbose output
  -h, --help             Show this help



Sorting added in SeqFu 1.11.

To sort by filename (ascending alphabetical order) add --sort filename. Numerical values are sorted from the largest (descending), supported values are:

  • n50, n75 or N90
  • count or counts (number of reads)
  • sum or tot (total bases)
  • min or minimum (minimum length)
  • max or maximum (maximum length)
  • avg or mean (average length)
  • aun (area under the Nx curve)

NOTE Specifying an invalid key will result in unsorted results with a warning, but in future releases this might throw an error.

Example output

Output is a TSV text with three columns (or CSV using --csv):


Screen friendly output

When using -n (--nice) output:

seqfu stats data/filt.fa.gz  -n
│ File            │ #Seq  │ Total bp │ Avg   │ N50 │ N75 │ N90 │ auN   │ Min │ Max │
│ data/filt.fa.gz │ 78730 │ 24299931 │ 308.6 │ 316 │ 316 │ 220 │ 0.385 │ 180 │ 485 │

MultiQC output

Using the --multiqc OUTPUTFILE option it's possible to save a MultiQC compatible file (we recommend to use the projectname_mqc.tsv filename format). After coolecting all the MultiQC files in a directory, using multiqc -f . will generate the MultiQC report. MultiQC itself can be installed via Bioconda with conda install -y -c bioconda multiqc.

To understand how to use MultiQC, if you never did so, check their excellent documentation.


The pre 1.11 version of the statistics has been made available via seqfu oldstats. There are no breaking changes at the moment, and an expanded set of tests ensures the compatibility not only of the metrics (unchanged) but also of the output (now supporting sorting options).


A similar functionality is provided by SeqKit, so we compared the performance of SeqFu with SeqKit and n50, both available from bioconda. We used a Linux Virtual Machine running Ubuntu 18.04, with 8 cores and 64 Gb of RAM for the test, with Miniconda (4.9.2) to install the required tools.

:warning: SeqKit, by default, omits N50 calculation, that is a core feature (always enabled) in SeqFu. The correct comparison is thus between seqfu stats and seqkit stats --all.

Speed evaluate with hyperfine, peak memory usage with this bash script.

As dataset we used the Human Genome (see this benchmark page), which contains few large sequences, and the reference genome of the gastrointestinal tract, which is composed by many short sequences instead.

The test can be replicated with these commands:

# Download tools (can be done in a new environment)
conda install -c conda-forge -c bioconda hyperfine n50=1.3.0 seqkit=0.16.0 seqfu=0.9.6
# Download datasets: many short sequences and few large sequences 

# Compare execution times

for FILE in $FILE1 $FILE2; do
  hyperfine --export-markdown stat_$(basename $FILE | cut -f1 -d.).md --warmup 1 --min-runs 3 \
    "seqfu stats $FILE" \
    "seqkit stats $FILE" \
    "seqkit stats --all $FILE" \
    "n50 -x $FILE" 

The result, for the Human Genome (few large sequences), has been:

Command Mean [s] Min [s] Max [s] Relative
seqfu stats $FILE 27.420 ± 0.349 27.090 27.785 1.00
seqkit stats $FILE :warning: 116.693 ± 0.236 116.512 116.960 4.26 ± 0.05
seqkit stats --all $FILE 120.435 ± 0.434 120.054 120.907 4.39 ± 0.06
n50 -x $FILE 34.888 ± 0.628 34.167 35.316 1.27 ± 0.03

For the Gastrointestinal reference genomes (many short sequences):

Command Mean [s] Min [s] Max [s] Relative
seqfu stats $FILE 6.885 ± 0.307 6.602 7.211 1.82 ± 0.09
seqkit stats $FILE :warning: 3.793 ± 0.082 3.699 3.854 1.00
seqkit stats --all $FILE 7.667 ± 0.081 7.583 7.746 2.02 ± 0.05
n50 -x $FILE 76.377 ± 1.990 74.891 78.638 20.14 ± 0.68


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