How to convert Geom object from PostGis in R in latitude and longitude?

Question

I have a database that has "location" attribute and it is saved as geom object and looks like this: 0101000020E6100000000000603D1D5EC0000000A06D424740

Is there a way to extract coordinates from it in R? These values are loaded in R as strings. Also it gave a warning:

Warning message:
In postgresqlExecStatement(conn, statement, ...) :
  RS-DBI driver warning: (unrecognized PostgreSQL field type geometry (id:18832) in column 2)

Any help appreciated.

Answer 1

Have you tried using the rgeos functions? One option would be reading WKT directly from the database (using ST_AsText )...

SELECT ST_AsText('0101000020E6100000000000603D1D5EC0000000A06D424740');
                st_astext                 
------------------------------------------
 POINT(-120.456871032715 46.518970489502)
(1 Zeile)

In R, using readWKT you can then extract the coordinate pair:

> readWKT("POINT(-120.456871032715 46.518970489502)")
SpatialPoints:
          x        y
1 -120.4569 46.51897
Coordinate Reference System (CRS) arguments: NA 

Another option would be to read x,y directly from the database using ST_X and ST_Y :

 SELECT ST_X('0101000020E6100000000000603D1D5EC0000000A06D424740'),
        ST_Y('0101000020E6100000000000603D1D5EC0000000A06D424740');
       st_x        |      st_y       
-------------------+-----------------
 -120.456871032715 | 46.518970489502
(1 Zeile)

Answer 2

I see that Jim Jones answer used mainly postgis and not R. The SF package allows for the conversion of Well Known Binary (WKB) to a simple features column (sfc), which in turn can be converted to coordinates.
st_as_sfc documentation
code:

library(sf)
#> Warning: package 'sf' was built under R version 4.0.3
#> Linking to GEOS 3.8.0, GDAL 3.0.4, PROJ 6.3.1
wkb = structure(list("0101000020E6100000000000603D1D5EC0000000A06D424740"), class = "WKB")
st_as_sfc(wkb,EWKB = TRUE) %>% st_coordinates()
#>           X        Y
#> 1 -120.4569 46.51897