(This article was first published on Blag's bag of rants, and kindly contributed to R-bloggers)
Since I joined SAP around 2 years ago, I simply stopped using ABAP…even when I use it for almost 11 years when I was a consultant…
A week ago, I was thinking about writing a new blog…something nice…some hacky…something that would allow me to just rest and don’t blog for the rest of the year…
I thought about ERP and R…while some things have been done already like Analytics with SAP and R from Piers Harding. I wanted to actually call R from the ERP instead of the ERP from R -;)
While thinking about this…I thought the best way to do it would be to reuse something that I before on my blog Consuming R from SAP Mobile Platform where I used Rook on Heroku to create a REST page that could be consumable…
So…for this particular blog…I wanted to something simple…call R, generate a graphic and show it on my ABAP program…here’s a small diagram to get things a little bit more clear…
Of course, when I tried this the first time…it failed…miserably…simply because the current implementation of Rook on Heroku doesn't have graphic capabilities on it…so it was impossible to actually generate a graphic…
Let’s get our hands dirty and let’s separate this blogs into steps so it become easier to handle -:)
Compile R with graphic capabilities on Heroku
This step was really a pain…it took me almost a week to get it done…and funny enough the rest of the steps took me about 6 hours…anyway…let’s keep going…
I started by looking at this two awesome projects on Github…rookonheroku and heroku-buildpack-r-build-r I took some chips from both and then create my own script and steps…
If you don’t have Heroku Tool Belt installed…go ahead and grab it…Log into Heroku and do the following…
Steps to install R on Heroku with graphic capabilities
Here's the code for the installR.sh script...
installR.sh
With that…you will have a full R installation with graphic capabilities…of course…you will need to delete all the garbage generated…but we will get there later…
Now…we need to install Rook…but we need version 1.0-2 so we need to download it and install it from the source…
Download Rook 1.0-2
Then launch R…simply call it by saying…
Calling R
As it will launch the R environment…
Installing Rook
As I was lazy to work more on the script to delete those files automatically…basically…the “bin” folder should look like this…
And the “vendor” folder like this…
Please remove the folders by using…
Removing folders
Once we’re done…we need to pack our stuff and sent it somewhere else, as Heroku is read only…once we log off…we lost everything…
Backup your work
Once we have everything saved…we can close the Heroku session and keep going…we can use WinSCP to copy our packed folders from our AWS server into our local project folder…uncompressed them and copy the following files from rookonheroku…
config.ru
demo.R
Procfile
Then…you can simply send everything back to Heroku…
Last push on Heroku
Of course…this is a lot of work…and I mean it…lot
So…I have upload the final compiled version to GitHub -;) To get it…simply do this…
Getting Blagrook
Create the code for the Rook application
On last thing we need to do…is to create the Rook application that it’s going to work on our Rook server…
demo.R
In a few words what is happening here is simple...we receive the parameters "carrid" and "seats"...both came as a string with "," so we use strsplit to separate them and then create a factor with the values. In the case of "seats" we need it to be numeric so we use the as.numeric function. Finally we create a data.frame combining "carrid" and "seats". Using "Cairo" (That's why we needed graphic capabilities on R) we create a Bitmap file which is going to be the result of creating a dotchart. Once it has been created, we read it, using the readBin function we get it's Hexadecimal representation. Using the function paste and its collapse method, we put everything on a big string and send it back...easy as pie -;)
I’m sure that you will wonder how I came out with the number 231488 on the readBin line…well…I download a nice Hexadecimal Editor called HxD then I create the graphic on my local R and load it…the I went to the last line and took the Hex number…
Using the calculator I simply changed the Hex value 38830 to decimal, multiply it by 16 and then add 16 more as the first line doesn’t count…simply and easy -;)
Create the function module ZUPLOAD_GRAPHICS_TABLE
This function module will allow us to upload the generated graphic into SE78.
ZUPLOAD_GRAPHICS_TABLE
Create the ABAP program to make it all happen…
ZROOK
When we run our program…we will call our Rook application on Heroku, which will receive the sum of seats for three carriers and then create a graphic, read it’s hexadecimal representation, give back to ABAP which will in turn create it on SE78 and then read it to show it on screen…now…you will not get the best resolution ever…and will assume it’s because “Cairo” doesn’t really support bmp files, or because the graphic is getting transported and changed all the way…so…it doesn't look good…but heck! We’re calling R from the ERP…what else do you want? -:D
It was really fun…so see you next year -;)
Greetings,
Blag.
Developer Experience.
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