darkr

darkr is an R package that wraps Trevas, a Java VTL engine.

What is VTL ?

VTL is a standard language for defining validation and transformation rules (set of operators, their syntax and semantics) for any kind of statistical data

For more information, follow this.

How to use it?

darkr will be available on CRAN as soon as a sufficiently large set of features is developed and tested.

For now, you need to clone this repository, open the project in RStudio, then load the package using devtools::load_all().

You could also install it via devtools::install_github("romaintailhurat/darkr").

Once done, try:

res <- darkr::vtl_eval("a := 3 * 3; b := 33; c := a + b;")
# 42

You can also use a VTL expression over a dataframe:

df <- darkr:::mock_df()
# names(df)
# [1] "id"   "name" "age"
ds <- darkr::df_to_ds(df)
new_ds <- darkr::vtl_eval("new_ds := ds[ drop age ];", ds)
new_df <- darkr::ds_to_df(new_ds)
# names(new_df)
# [1] "id"   "name"

Limits

This is a work in progress, some important parts are missing:

• we create a VTL identifier based on column names id or name if they exist, overriding is not possible,
• multiple bindings are not supported,
• the Java implementation of a dataset currently used is very basic, it is probably not intended to be on par with native R performance.

Roadmap

• [x] Basic wrapping of Trevas
• [x] Dataframes operations :
  • [x] basic support of Trevas dataset operations
  • [x] transformation function from a dataframe to a Trevas dataset
  • [x] back from a dataset to a dataframe
• [ ] Evaluation
  • [ ] Support multiple bindings when evaluating a VTL expression
  • [ ] Directly support R values for bindings (eg data frames)
  • [ ] Implement a VTL expression builder
• [ ] Benchmarking
  • [ ] Compare pure R operations VS Trevas

How to developp?

TODO

Java dependency

For now, in order to include Trevas as a jar, you need to clone the GitHub repo, and produce the jar file using mvn package and then copy it.

In two steps :

cd ~/code/vtl/Trevas/vtl-engine/
mvn package

then:

cd ~/code/vtl/darkr/
cp ../Trevas/vtl-engine/target/vtl-engine-0.1.0-jar-with-dependencies.jar ./java/

Why the name?

Because the package is using Trevas, the Java VTL engine, and trevas means "darkness" in Portuguese.