In a previous blog post I showed you how create and display a ggplot2 R graphic using SQL. Make sure to check it out before reading the rest of this blog post.
In my previous blog post, I showed and mentioned that the PNG graphic returned by the embedded R execution SQL statement was not the same as what was produced if you created the graphic in an R session.
Here is the same ggplot2 graphic. The first one is what is produced in an R session and the section is what is produced by SQL query and the embedded R execution in Oracle.
As you can see the second image (produced using the embedded R execution) gives a very square image.
The reason for this is that Oracle R Enterprise (ORE) creates the graphic image in PNG format. The default setting from this is 480 x 480. You will find this information when you go digging in the R documentation and not in the Oracle documentation.
So, how can I get my ORE produced graphic to appear like what is produced in R?
What you need to do is to change the height and width of the PNG image produced by ORE. You can do this by passing parameters in the SQL statement used to call the user defined R function, that in turn produces the ggplot2 image.
In my previous post, I gave the SQL statement to call and produce the graphic (shown above). One of the parameters to the rqTableEval function was set to null. This was because we didn’t have any parameters to pass, apart from the data set.
We can replace this null with any parameters we want to pass to the user defined R function (demo_ggpplot). To pass the parameters we need to define them using a SELECT statement.
cursor(select 500 as "ore.png.height", 850 as "ore.png.width" from dual),
The full SELECT statement now becomes
select * from table(rqTableEval( cursor(select * from claims), cursor(select 500 as "ore.png.height", 850 as "ore.png.width" from dual), 'PNG', 'demo_ggpplot'));
When you view the graphic in SQL Developer, you will get something that looks a bit more like what you would expect or want to see.
For each graphic image you want to produce using ORE you will need to figure out that are the best PNG height and width settings to use. Plus it also depends on what tool or application you are going to use to display the images (eg. APEX etc)