✎ calculaterexpression [Dinamica EGO]

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======= Calculate R Expression =======
The functor 'Calculate R Expression' allows Dinamica EGO to call R externally and process the script outputs as if they were
part Dinamica itself. 

====== Setup ======

There are two ways to setup the 'Calculate R Expression' functor:\\
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=== R Plugin ===
There is a plugin that contains everything needed to wrap R scripts inside Dinamica EGO, just extract [[http://csr.ufmg.br/~romulo/R.7z|this file]]
 to your Dinamica EGO installation directory (usually c:\Program Files\Dinamica EGO) and you will be good to go.\\
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=== Local R Installation ===
Users can specify a local R installation to be used 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 directory\\bin' subdirectory.
  - [[externalcommunication|Dinamica package]] for R must be installed and at the latest version.

To specify your custom R installation, go to Tools -> Options -> External Comm tab and select 'Use alternative R installation for Calculate R Expression':
{{:dinamica_options_use_alternative_r_install.png?nolink|}}
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====== Usage ======
The functor is available under the 'External Communication' tab at the library.\\
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=== 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 (will be passed as a list containing two named members, 'Keys' and 'Values' - only **LookupTable**'s are supported at this time)
  * 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:\\
<code>
# Will store the 5th key from the passed LookupTable in the variable 'testing'
testing <- t1$Keys[ 5 ];

# Store the second passed String.
secondString <- s2;

# Store the 10th passed Value.
tempNumber <- v10;
</code>
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=== 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 ) |
In the examples above, data was constructed inside the calling functions. You can also specify variables as parameters. 
<note important>All output functions require a identifier as the first parameter, that's the name Dinamica uses for retrieving the correct data.</note>
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Keep in mind:\\
  * You can pass any kind of numeric value on the outputDouble function.
  * Collections of numbers are valid Number Vector's.
  * A LookupTable requires **2** number vectors, one for the Keys and another for the Values. Both vectors must have the same number of elements.
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====== Example Scripts ======
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=== Multiply each value of the passed LookupTable by itself. ===
{{ ::ex1_calculate_r.png?nolink |}}
Expression:
<code>
for ( i in 1:length( t1$Values ) ) {
  tempValue <- t1$Values[ i ];
  t1$Values[ i ] = tempValue * tempValue;
}

outputLookupTable( "poweredTable", t1$Keys, t1$Values );
</code>
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=== Extract the mean of passed LookupTable values. ===
{{ ::ex2_calculate_r.png?nolink |}}
Expression:
<code>
tableMean <- mean( t1$Values );
print( paste( "Mean is", tableMean ) );
outputDouble( "mean", tableMean );
</code>
Noticed the **print()** statement? Dinamica EGO's Message Log will show output messages from the R script.
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=== Plot passed LookupTable to an image on the path specified by passed String ===
{{ ::ex3_calculate_r.png?nolink |}}
Expression:
<code>
outputFile  <- s1;
print( paste( "Plotting to", outputFile ) );
jpeg( outputFile, quality=100 );
plot( t1 );
dev.off();
</code>