Using R in PostgreSQL
Contents
Perhaps a Simpler Alternative
Aggregate functions in PostgreSQL: https://www.postgresql.org/docs/9.0/static/functions-aggregate.html
Joe Conway's Documentation on pl/r
http://joeconway.com/doc/plr-US.pdf http://www.joeconway.com/plr/doc/plr-funcs.html http://www.joeconway.com/plr/doc/plr-window-funcs.html
Sample Function Code in PostgreSQL
Creating the Sample Function
Inside a database (ex) tigertest):
CREATE OR REPLACE FUNCTION r_max (integer, integer) RETURNS integer AS ’
if (arg1 > arg2)
return(arg1)
else
return(arg2)
’ LANGUAGE ’plr’ STRICT;
Calling the Sample Function
SELECT * FROM r_max(2,3);
returns
r_max
-------
3
(1 row)
hcllayerwinv table from tigertest database
Table "public.hcllayerwinv"
Column | Type | Collation | Nullable | Default
------------------+------------------------+-----------+----------+---------
place | character varying(100) | | |
statecode | character varying(2) | | |
year | integer | | |
layer | integer | | |
lcount | numeric | | |
nosingleton | bigint | | |
nomultiton | bigint | | |
nopair | bigint | | |
nohull | bigint | | |
totmultitoncount | numeric | | |
avgmultitoncount | numeric | | |
totpaircount | numeric | | |
avgpaircount | numeric | | |
totpairlength | double precision | | |
avgpairlength | double precision | | |
minpairlength | double precision | | |
maxpairlength | double precision | | |
tothullcount | numeric | | |
avghullcount | numeric | | |
tothullarea | double precision | | |
avghullarea | double precision | | |
minhullarea | double precision | | |
maxhullarea | double precision | | |
tothulldensity | double precision | | |
avghulldensity | double precision | | |
seedearlyinvf | double precision | | |
inflator | numeric | | |
seedearlyinvl16f | double precision | | |
Regress by
--By: place, statecode, layer, --Regress: seedearlyinvl16f ON nosingleton, totmultitoncount, totpaircount, tothullcount, avgpairlength, avghullarea, avghulldensity
Installing PL/R on the dbase server
Check the version of the dbase by doing a
SELECT version();
This gives us 9.5.10
Then as root:
apt-get install postgresql-9.5-plr
Finally enable the extension in a dbase:
create extension plr;
See also: http://www.joeconway.com/presentations/plr-PGConfNYC2014.pdf
Instructions on Use
To use R from pgAdmin III, follow the instructions in this tutorial: choose the database, click SQL, and run "CREATE EXTENSION plr;". This allows R functions to be used in this database from then on. You should be able to run the given examples in the tutorial after this is done. This was run on databases tigertest and template1.
Another possibly useful presentation on PL/R.
How PL/R was installed on the RDP
On 2018-01-18, PL/R was installed to allow PostgreSQL users to use R functions from SQL queries. It was installed using this tutorial. The link from the tutorial for PL/R doesn't work, I used this instead.
It required R version 3.3.0 for PL/R to work with PostgreSQL 9.5. If the environmental variables R_HOME or PATH are edited so that they point to a different version of R, this might not work, and PL/R might have to be reinstalled. If the version of PostgreSQL is updated, both the R version and PL/R version will have to match it as well.
