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dbcolhisto - compute a histogram over a column of Fsdb data


dbcolhisto [-ag] [-W BucketWidth] [-S BucketStart] [-E BucketEnd] [-N NumberOfBuckets] column


This program computes a histogram over a column of data. Records containing non-numeric data are considered null do not contribute to the stats (optionally they are treated as zeros).

Defaults to 10 buckets over the exact range of data. Up to three parameters (number of buckets, start, end, and width) can be specified, the rest default accordingly.

Buckets range from a value (given the the low column) to just below the next low value and buckets are equal width. If necessary, extra "<min" and ">max" buckets are created. By default, the last bucket includes max (and is thus infinitesimally larger than the other buckets). This irregularity can be removed with the -I option.

This program requires O(number of buckets) memory and O(size of data) temporary disk space.


-W or --width N

Gives with width of each bucket, in data units. Default is whatever gives 10 buckets over the whole range of data.

-S or --start N

Buckets start at value N, in data units. Default is the minimum data value.

-E or --end N

Buckets end at value N, in data units. Default is the maximum data value.

-N or --number N

Create N buckets. The default is 10 buckets.

-g or --graphical

Generate a graphical histogram (with asterisks). Default is numeric.

-I or --last-inclusive

Make the last bucket non-inclusive of the last value.


Compute stats over all records (treat non-numeric records as zero rather than just ignoring them). Default is non-numeric records are ignored.

-e EmptyValue or --empty

Specify the value any null bins get. (Default: -.)

This module also supports the standard fsdb options:


Enable debugging output.

-i or --input InputSource

Read from InputSource, typically a file name, or - for standard input, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.

-o or --output OutputDestination

Write to OutputDestination, typically a file name, or - for standard output, or (if in Perl) a IO::Handle, Fsdb::IO or Fsdb::BoundedQueue objects.

--autorun or --noautorun

By default, programs process automatically, but Fsdb::Filter objects in Perl do not run until you invoke the run() method. The --(no)autorun option controls that behavior within Perl.


Show help.


Show full manual.



    #fsdb name id test1
    a 1 80
    b 2 70
    c 3 65
    d 4 90
    e 5 70
    f 6 90


    cat DATA/grades.fsdb | dbcolhisto -S 0 -E 100 -N 10 test1


    #fsdb low histogram:q
    0       0
    10      0
    20      0
    30      0
    40      0
    50      0
    60      1
    70      2
    80      1
    90      2
    #  | dbcolhisto -S 0 -E 100 -N 10 test1


Fsdb, dbcolpercentile, dbcolstats


This program could run in constant memory with no external storage when the buckets are pre-specified. That optimization is not implemented.



    $filter = new Fsdb::Filter::dbcolhisto(@arguments);

Create a new dbcolhisto object, taking command-line arguments.



Internal: set up defaults.



Internal: parse command-line arguments.



Internal: setup, parse headers.



Internal: run over each rows.


Copyright (C) 1991-2022 by John Heidemann <>

This program is distributed under terms of the GNU general public license, version 2. See the file COPYING with the distribution for details.