dbcolmovingstats - Man Page

compute moving statistics over a window of a column of data


dbcolmovingstats [-am] [-w WINDOW] [-e EmptyValue] [-k KEY] column


Compute moving statistics 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  with -a).

Statitics are computed over a WINDOW of samples of data.

[In progress 2020-11-12, but not completed: Alternatively, if a key column is given with -k KEY, then a we treat the key column as a time value and compute the time-weighted mean.]

Currently we compute mean and sample standard deviation. (Note we only compute sample standard deviation, not full population.) Optionally, with -m we also compute median. (Currently there is no support for generalized quantiles.)

Values before a sufficient number have been accumulated are given the empty value (if specified with -e). If no empty value is given, stats are computed on as many are possible if no empty value is specified.

Dbcolmovingstats runs in O(1) memory, but must buffer a full window of data. Quantiles currently will repeatedly sort the window and so may perform  poorly with wide windows.


-a or --include-non-numeric

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

-w or --window WINDOW

WINDOW of how many items to accumulate (defaults to 10). (For compatibility with fsdb-1.x, -n is also supported.)

-k or --key KEY

The KEY specifies a field that is used to evaluate the window---a window must span at most this range of value so the key field. (For example, if KEY is the time and window is 60, then enough samples will be added to make at most 60s of observations. With a key, sampling can be irregular.) If key is specified, we also output a moving_n field  for how many samples are in each window.

-m or --median

Show median of the window in addition to mean.

-e E or --empty E

Give value E as the value for empty (null) records. This null value is then output before a full window is accumulated.

-f FORMAT or --format FORMAT

Specify a printf(3)-style format for output mean and standard deviation. Defaults to %.5g.

Eventually we expect to support other options of dbcolstats.

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.

Sample Usage


    #fsdb date  epoch count
    19980201        886320000       6
    19980202        886406400       8
    19980203        886492800       19
    19980204        886579200       53
    19980205        886665600       20
    19980206        886752000       18
    19980207        886838400       5
    19980208        886924800       9
    19980209        887011200       22
    19980210        887097600       22
    19980211        887184000       36
    19980212        887270400       26
    19980213        887356800       23
    19980214        887443200       6


    cat data.fsdb | dbmovingstats -e - -w 4 count


        #fsdb date epoch count moving_mean moving_stddev
        19980201        886320000       6       -       -
        19980202        886406400       8       -       -
        19980203        886492800       19      -       -
        19980204        886579200       53      21.5    21.764
        19980205        886665600       20      25      19.442
        19980206        886752000       18      27.5    17.02
        19980207        886838400       5       24      20.445
        19980208        886924800       9       13      7.1647
        19980209        887011200       22      13.5    7.8528
        19980210        887097600       22      14.5    8.8129
        19980211        887184000       36      22.25   11.026
        19980212        887270400       26      26.5    6.6081
        19980213        887356800       23      26.75   6.3966
        19980214        887443200       6       22.75   12.473
        #   | dbcolmovingstats -e - -n 4 count

See Also

Fsdb. dbcolstats. dbmultistats. dbrowdiff.


Currently there is no support for generalized quantiles.


2021-01-27 perl v5.32.1 User Contributed Perl Documentation