pg_median_utils 0.0.1
=============


A postgres extension containing some median-related utilities.

At this time, provides two window functions - one for applying a median filter, which behaves the same as SciPy's [medfilt](https://docs.scipy.org/doc/scipy-0.14.0/reference/generated/scipy.signal.medfilt.html), and a second which applies the median filter iteratively until it converges (no change greater than some small value). 

Usage
-----

Use with any double precision column, for example:

    SELECT median_filter(v::double precision, 5) over() FROM generate_series(1, 10) as t(v);
    
    iterated_median_filter 
    ------------------------
                          1
                          2
                          3
                          4
                          5
                          6
                          7
                          8
                          8
                          8
    (10 rows)

Or for an iterated version:

    SELECT iterated_median_filter(v, 3) over() FROM (VALUES (1), (1.1), (0.9), (1.1), (0.95), (2.1), (1.95), (2.0), (2.05), (3.11), (2.99), (3.05), (3.0)) as t(v);
    
    iterated_median_filter 
    ------------------------
                          1
                          1
                          1
                        1.1
                        1.1
                       1.95
                          2
                          2
                       2.05
                       2.99
                          3
                          3
                          3
    (13 rows)

Comparing the two:

    SELECT median_filter(v, 3) over(), iterated_median_filter(v, 3, 0.0000001) over() FROM (VALUES (1), (1.1), (0.9), (1.1), (0.95), (2.1), (1.95), (2.0), (2.05), (3.11), (2.99), (3.05), (3.0)) as t(v);
    
    median_filter | iterated_median_filter 
    ---------------+------------------------
                 1 |                      1
                 1 |                      1
               1.1 |                      1
              0.95 |                    1.1
               1.1 |                    1.1
              1.95 |                   1.95
                 2 |                      2
                 2 |                      2
              2.05 |                   2.05
              2.99 |                   2.99
              3.05 |                      3
                 3 |                      3
                 3 |                      3
    (13 rows)