Calculate R Expression

Description

The functor 'Calculate R Expression' allows Dinamica EGO to call R externally and process the script outputs as if they were part of Dinamica itself. For an overview of how Dinamica and R can be linked together check the documentation about R Coupling.

Inputs

Name	Type	Description
Expression	String Type	The expression that will run on R.
Treat Warning As Errors	Boolean Value Type	Warnings on R script will be considered errors.

Optional Inputs

None.

Output

Name	Type	Description
result	Struct Type	A struct containing the output values generated by the expression.

Group

Integration

Notes

There are two ways to setup the 'Calculate R Expression' functor:

Dinamica EGO Enhancement Plugin

Simply download and install the Dinamica EGO Enhancement Plugin. It contains everything you need to run R scripts inside Dinamica EGO.

Local R Installation

Additionally, users can specify and use their own local R installation for execution. The pre-requisites are:

R needs to be at least at the 3.3.1 version.

Rscript.exe must be valid and located at the <installation folder>/bin sub-folder.

Dinamica package for R must be installed and at the latest version.

To specify your custom R installation, go to Tools --> Options --> Integration tab and select Use alternative R installation for Calculate R Expression:

Usage

The functor is available under the Integration tab at the library.

R Script Inputs

To pass input parameters from Dinamica EGO to R, hooks must be placed to collect data. You can use the Create a hook button on the selected functor bar or drag the hooks individually. The valid hook types are:

Number Table

Number Value

Number String

To access the passed inputs on your R script, follow Dinamica EGO naming conventions and use t[0-99], v[0-99], s[0-99] for each type respectively. For example:

# Will store the 5th key from the passed Lookup Table in the variable 'testing' testing <- t1$Keys[ 5 ]; # Store the second passed String. secondString <- s2; # Store the 10th passed Value. tempNumber <- v10;

R Script Outputs

To output data back to Dinamica EGO, the user must call a set of functions designed for this functionality:

Function name	Output Data Type	Usage Example
outputDouble()	Real	outputDouble( “myDouble”, 3.14 )
outputNumberVector()	Tuple	outputNumberVector( “myTuple”, c(1:10) )
outputString()	String	outputString( “myString”, “This is a string” )
outputLookupTable()	LookupTable	outputLookupTable( “myLUT”, c(1:10), c(1:10) * 10 )
outputTable()	Table	outputTable( “myTable”, data.frame(State = c(“Massachusetts”, “Massachusetts”), City = c(“Boston”, “Chelsea”), Population = c(667137, 39398), stringsAsFactors = FALSE), 2 )

In the examples above, data was constructed inside the calling functions. You can also specify variables as parameters.

All output functions require an identifier as the first parameter, that's the name Dinamica uses for retrieving the correct data (to put into the struct output).

Keep in mind:

You can pass any kind of numeric value on the outputDouble function.

Collections of numbers are valid number vector's.

A Lookup Table requires 2 number vectors, one for the “Keys” and another for the “Values”. Both vectors must have the same number of elements.

The outputTable function requires a table, that can be constructed with data.frame R function. There is another parameter that is optional with default value 1, and it means how many Key columns the table has, from the leftmost column.

Notice the use of the stringAsFactors = FALSE flag. This flag prevents R from converting the passed strings to Factors(numbers).

Tables / Lookup Tables

Tables or Lookup Tables can be transferred to R using the Number Table functor. When dealing with each of these types extra caution must be taken:

Lookup Tables

Lookup Tables are transferred to R as a List with two columns, “Keys” and “Values”.

Each column can be individually accessed by using the $ operator, for example:

t1$Keys[ 1 ] will access the first key of the Lookup Table t1.

t2$Values[ 2 ] will access the second value of the Lookup Table t2

Tables

Tables are transferred to R as a DataFrame type variable. Each column can be individually accessed by using the $ operator, just like Lookup Tables. Please check this page for more information on how to deal with Tables. The rules for them in Calculate R Expression are the same as sending and receiving through External Communication.

Example Scripts

Multiply each value of the passed Lookup Table by itself

Expression:

for ( i in 1:length( t1$Value ) ) { tempValue <- t1$Value[ i ]; t1$Value[ i ] = tempValue * tempValue; } outputLookupTable( "poweredTable", t1$Key, t1$Value );

Extract the mean of passed Lookup Table values

Expression:

tableMean <- mean( t1$Values ); print( paste( "Mean is", tableMean ) ); outputDouble( "mean", tableMean );

Noticed the print() statement? Dinamica EGO's Message Log will show output messages from the R script (as Result's).

Plot passed Lookup Table to an image on the path specified by passed String

Expression:

outputFile <- s1; print( paste( "Plotting to", outputFile ) ); jpeg( outputFile, quality=100 ); plot( t1 ); dev.off();

Internal Name

CalculateRExpression