This topic describes the ST_LineSubstring function. This function returns the substring of a LineString object.
Syntax
geometry ST_LineSubstring(geometry aLinestring , float8 startfraction , float8 endfraction);
geography ST_LineSubstring(geography aLinestring , float8 startfraction , float8 endfraction);Parameters
Parameter | Description |
aLinestring | The LineString object that you want to specify. |
startfraction | The start position. |
endfraction | The end position. |
Description
If the startfraction and endfraction parameters are set to the same value, this function serves the same as the ST_LineInterpolatePoint function.
Before you can obtain the substring of a MultiLineString object, you must use the ST_LineMerge function to merge the LineStrings of the MultiLineString object.
The ST_LineSubstring function supports 3D objects and does not delete z coordinates.
The ST_LineSubstring function supports m coordinates.
Examples
SELECT ST_AsText(ST_LineSubstring('LINESTRING(0 0,10 10)'::geometry,0.3,0.6));
st_astext
---------------------
LINESTRING(3 3,6 6)
(1 row)
--geography
SELECT ST_AsText(ST_LineSubstring('LINESTRING(0 0,10 10)'::geography,0.3,0.6));
st_astext
--------------------------------------------------------------------------------
LINESTRING(2.97227762767668 3.01417970957332,5.96094221033023 6.0199989936211)