PostGIS

ST_Distinct4ma

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12.13. Built-in Map Algebra Callback Functions

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Name

ST_Distinct4ma — Raster processing function that calculates the number of unique pixel values in a neighborhood.

Synopsis

float8 +`*`+ST_Distinct4ma*(`float8[][] `matrix, text nodatamode, text[] VARIADIC args`)`;

double precision +`*`+ST_Distinct4ma*(`double precision[][][] `value, integer[][] pos, text[] VARIADIC userargs`)`;

Description

Calculate the number of unique pixel values in a neighborhood of pixels.

Note

Variant 1 is a specialized callback function for use as a callback parameter to ST_MapAlgebraFctNgb.
Note

Variant 2 is a specialized callback function for use as a callback parameter to ST_MapAlgebra (callback function version).
Warning

Use of Variant 1 is discouraged since ST_MapAlgebraFctNgb has been deprecated as of 2.1.0.

Availability: 2.0.0

Enhanced: 2.1.0 Addition of Variant 2

Examples

SELECT
    rid,
    st_value(
        st_mapalgebrafctngb(rast, 1, NULL, 1, 1, 'st_distinct4ma(float[][],text,text[])'::regprocedure, 'ignore', NULL), 2, 2
    )
FROM dummy_rast
WHERE rid = 2;
 rid | st_value
-----+----------
   2 |        3
(1 row)

See Also

ST_MapAlgebraFctNgb, ST_MapAlgebra (callback function version), ST_Min4ma, ST_Max4ma, ST_Sum4ma, ST_Mean4ma, ST_Distinct4ma, ST_StdDev4ma

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