Introductory Example
Data is plotted by passing an sql query to the plot() function.
Let's consider an example based on a table of air quality data from R's data library.
robert=# select * from airquality limit 10;
id | ozone | solar_r | wind | temp | month | day
----+-------+---------+------+------+-------+-----
1 | 41 | 190 | 7.4 | 67 | 5 | 1
2 | 36 | 118 | 8 | 72 | 5 | 2
3 | 12 | 149 | 12.6 | 74 | 5 | 3
4 | 18 | 313 | 11.5 | 62 | 5 | 4
5 | | | 14.3 | 56 | 5 | 5
6 | 28 | | 14.9 | 66 | 5 | 6
7 | 23 | 299 | 8.6 | 65 | 5 | 7
8 | 19 | 99 | 13.8 | 59 | 5 | 8
9 | 8 | 19 | 20.1 | 61 | 5 | 9
10 | | 194 | 8.6 | 69 | 5 | 10
(10 rows)
A scatter plot is generated by passing a query to the plot command which has two numeric columns in the result set.
robert=# select plot('select wind::numeric,
temp::numeric from airquality limit 20'
) as "air quality scatter plot";
air quality scatter plot
--------------------------------------------------
+
74 ++A--+----+----+-A---+----+----+----+---++ +
+ + + + + + + + + +
72 ++ A ++ +
70 ++ ++ +
| A A | +
68 ++ A AA ++ +
66 ++ A A A ++ +
| A | +
64 ++ A ++ +
62 ++ A A ++ +
| A | +
60 ++ ++ +
58 ++ A A ++ +
+ + + + + + +A + + +
56 ++---+----+----+-----A----+----+----+---++ +
6 8 10 12 14 16 18 20 22+
wind
(1 row)
The same plot can be prepared for display on the web by changing the terminal parameter.
robert =# set plotpg.terminal = 'svg';
SET
robert =# select plot('select wind::numeric,
temp::numeric
from airquality limit 20'
) as "air quality scatter plot";
<?xml version="1.0" encoding="utf-8" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
...
Terminal can also be set to 'png' for image data.