ST_HMTAsArray
將熱力圖瓦片轉(zhuǎn)換為基于數(shù)組矩陣的表示方法,方便進(jìn)行查看。
語法
float8[][] ST_HMTAsArray(bytea hmt);
返回值
返回一個二維的float8數(shù)組,每一個值代表熱力圖的統(tǒng)計值。
參數(shù)
參數(shù)名稱 | 描述 |
hmt | 基于protobuf表示的HMT二進(jìn)制。 |
描述
將熱力圖瓦片轉(zhuǎn)換為基于數(shù)組矩陣的表示方法,方便進(jìn)行查看。 熱力圖瓦片需要通過ST_AsHMT函數(shù)生成。
示例
CREATE TABLE test_table AS
SELECT i num,
ST_setSRID(st_makepoint((i-0.5)::numeric, (i-0.5)::numeric), 4326) geom,
i*100::int4 weight,
i*i*i::float8 volume
FROM generate_series(1, 10) i;
SELECT ST_HMTAsArray(ST_AsHMT(geom, --geometry type
ST_MakeEnvelope(0, 0, 10, 10, 4326), -- Extent
10, -- Width, in pixel
10 -- height
))
FROM test_table;
---------
[0:9][0:9]={{1,0,0,0,0,0,0,0,0,0},{0,1,0,0,0,0,0,0,0,0},{0,0,1,0,0,0,0,0,0,0},{0,0,0,1,0,0,0,0,0,0},{0,0,0,0,1,0,0,0,0,0},{0,0,0,0,0,1,0,0,0,0},{0,0,0,0,0,0,1,0,0,0},{0,0,0,0,0,0,0,1,0,0},{0,0,0,0,0,0,0,0,1,0},{0,0,0,0,0,0,0,0,0,1}}
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