The three aggregate functions for temporal circular buffers are illustrated next.
Temporal count
tCount(tcbuffer) → {tintSeq,tintSeqSet}
WITH Temp(temp) AS (
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.1)@2001-01-01,
Cbuffer(Point(1 1), 0.3)@2001-01-03)' UNION
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.2)@2001-01-02,
Cbuffer(Point(1 1), 0.4)@2001-01-04)' UNION
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.3)@2001-01-03,
Cbuffer(Point(1 1), 0.5)@2001-01-05)' )
SELECT tCount(Temp)
FROM Temp;
-- {[1@2001-01-01, 2@2001-01-02, 1@2001-01-04, 1@2001-01-05)}
Window count
wCount(tcbuffer) → {tintSeq,tintSeqSet}
WITH Temp(temp) AS (
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.1)@2001-01-01,
Cbuffer(Point(1 1), 0.3)@2001-01-03)' UNION
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.2)@2001-01-02,
Cbuffer(Point(1 1), 0.4)@2001-01-04)' UNION
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.3)@2001-01-03,
Cbuffer(Point(1 1), 0.5)@2001-01-05)' )
SELECT wCount(Temp, '1 day')
FROM Temp;
/* {[1@2001-01-01, 2@2001-01-02, 3@2001-01-03, 2@2001-01-04, 1@2001-01-05,
1@2001-01-06)} */
TODO Temporal centroid
tCentroid(tcbuffer) → tgeompoint
WITH Temp(temp) AS (
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.1)@2001-01-01,
Cbuffer(Point(1 1), 0.3)@2001-01-03)' UNION
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.2)@2001-01-01,
Cbuffer(Point(1 1), 0.4)@2001-01-03)' UNION
SELECT tcbuffer '[Cbuffer(Point(1 1), 0.3)@2001-01-01,
Cbuffer(Point(1 1), 0.5)@2001-01-03)' )
SELECT astext(tCentroid(Temp))
FROM Temp;
/* {[POINT(72.451531682218 76.5231414472853)@2001-01-01,
POINT(55.7001249027598 72.9552602410653)@2001-01-03)} */