How do I make a polygon from LineString?

Question

I am trying to create a polygon using Lat/long's of community districts. Here is my query below:

SELECT ST_MakePolygon(ST_GeomFromText(
'LINESTRING (40.665535 -73.9933, 40.665535 -73.969749, 40.7245 73.9419, 40.6773 74.0094,40.6795 73.9992, 40.6733 -73.9903, 40.7081  -73.9571, 40.6872 -73.9418, 40.6849 -73.9845, 40.665535 -73.9933)'), 4326);

Whenever I try to run this query I get an error message:

HINT: No function matches the given name and argument types. You might need to add explicit type casts.

Can someone guide me in the right direction?

Answer 1

If you are using Well Known Text (WKT) you probably want to describe it as a polygon.

It would look like:

SELECT ST_GeomFromText('POLYGON((40.665535 -73.9933, 40.665535 -73.969749, 40.7245 73.9419, 40.6773 74.0094, 40.6795 73.9992, 40.6733 -73.9903, 40.7081 -73.9571, 40.6872 -73.9418, 40.6849 -73.9845, 40.665535 -73.9933))', 4326);

The reason why there are two brackets (rather than one for the LINESTRING case) is that polygons can have interior regions excluded - it would then have "holes".

Also, I've done the same order of coordinates as your question. However you might be surprised by the results, because that area is not in the USA. It is somewhere in Antarctica, south of the Indian Ocean. For your case, WKT is longitude, latitude rather than latitude, longitude. Think Cartesian plane (X, then Y).

Answer 2

You have your brackets all mixed up. Put the SRID inside the st_geomfromtext bracket and you should be set