Example
=# create table data (x int, y int);
=# insert into data values (1, 1), (2, 2), (3, 3), (4, 4);
=# select plot('select x, y from data');
plot
-------------------
<?xml version="1.0" encoding="utf-8"....
<svg>....
Or plot directly in psql.
=# select plot('select x, y from data', 'set style data lines;');
plot
-------------------------------------------------------------------------------------------------------------
+
5 ++-----------+-----------+------------+-----------+------------+-----------+------------+--------****+
+ + + + + + + + ****** ++
4.5 ++ ****** +++
| ****** |+
4 ++ ****** +++
| ***** |+
| ***** |+
3.5 ++ ***** +++
| ***** |+
3 ++ ****** +++
| ****** |+
2.5 ++ ****** +++
| ****** |+
2 ++ ****** +++
| ***** |+
| ***** |+
1.5 ++ ***** +++
+ ***** + + + + + + + ++
1 ***----------+-----------+------------+-----------+------------+-----------+------------+----------+++
1 1.5 2 2.5 3 3.5 4 4.5 5+
x +
+
(1 row)
Different result sets, different plots.
The characteristics of the result set will determine plot types. Documentation
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Why plot in the database?
"That's where the data is." But really, no particular reason.
Plotpg was developed for an a custom charting facility in pgantenna.