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--- calculate_r_expression [2018/09/03 14:24]
francisco [R Script Outputs]
+++ calculate_r_expression [2026/07/22 18:13] (current)
hermann
@@ Line 3: / Line 3: @@
 ===== 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 [[reference_book:r_coupling|R Coupling]].
+This is a **[[ego_script#container_functors|container functor]]** that calls R externally with the user-defined expression. Like the other calculator functors, data is connected through hook functors placed inside its ''<nowiki>{{ … }}</nowiki>'' block.
 ===== Inputs =====
-^ Name  ^ Type  ^ Description  ^
+^ Name ^ Type ^ Description ^
-| Expression  | [[String Type]]  | The expression that will run on R.  |
+| Expression | [[ego_script#constants|Code]] | The expression that will run on R. ''Code'' values cannot be written as plain text constants in EGO Script — see [[#writing_the_expression_in_ego_script|Writing the expression in EGO Script]] below. |
-| Treat Warning As Errors  | [[Boolean Value Type]]  | Warnings on R script will be considered errors.  |
+| Treat Warning As Errors | [[Boolean Value Type]] | Warnings raised by the R script will be treated as errors. |
 ===== Optional Inputs =====
@@ Line 15: / Line 15: @@
 None.
-===== Output =====
+===== Outputs =====
-^ Name  ^ Type  ^ Description  ^
+^ Name ^ Type ^ Description ^
-| result  | [[Struct Type]]  | A struct containing the output values generated by the expression.  |
+| result | [[struct_type|Struct]] | A struct containing the output values generated by the expression. |
-===== Group =====
-[[Functor List#Integration | Integration]]
 ===== Notes =====
-There are two ways to setup the 'Calculate R Expression' functor:
+==== Expression inputs ====
-==== Dinamica EGO Enhancement Plugin ====
+Data is passed into the expression through **hook** functors placed inside the container's ''<nowiki>{{ … }}</nowiki>'' block — the same [[ego_script#verbose_form|verbose form]] hook mechanism used by the calculator functors. Hooks can be added using the //Create a hook// button on the functor bar, or by dragging them in individually.
-Simply download and install the [[plugins_4|Dinamica EGO Enhancement Plugin]]. It contains everything you need to run R scripts inside Dinamica EGO.
+  * Tables and lookup tables → [[Number Table]] → available in R as ''t1'', ''t2'', …, ''t100''
+  * Scalar values → [[Number Value]] → available as ''v1'', ''v2'', …, ''v100''
+  * Strings → [[Number String]] → available as ''s1'', ''s2'', …, ''s100''
-==== Local R Installation ====
+Maps cannot be connected — this functor has no cell context. There is no shorthand notation; see [[calculate_functors|Calculate Functors — Complete Operator Documentation]] for the general hook mechanism and syntax.
-Additionally, users can specify and use their own local R installation for execution. The pre-requisites are:
+=== Tables and lookup tables ===
-  * R needs to be at least at the 3.3.1 version.
+Lookup tables and tables require extra care, since each is transferred to R using a different representation.
-  * ''Rscript.exe'' must be valid and located at the ''<installation folder>/bin'' sub-folder.
+A **lookup table** is transferred as a list with two columns, ''Key'' and ''Value''. Each column is accessed with the ''$'' operator:
-  * [[external communication|Dinamica package]] for R must be installed and at the latest version.
+<code rsplus>
+# Access the third key and its corresponding value in lookup table t1
+patchId <- t1$Key[3];
+patchArea <- t1$Value[3];
+</code>
-To specify your custom R installation, go to Tools --> Options --> Integration tab and select //Use alternative R installation for Calculate R Expression//:
+A **table** is transferred as a [[https://en.wikibooks.org/wiki/R_Programming/Working_with_data_frames|DataFrame]], with each column likewise accessed using ''$''. Two conventions apply to tables in either direction:
-{{:dinamica_options_use_alternative_r_install.png?nolink|}}
+  * **Key columns** are marked by an asterisk (''*'') appended to their column name — this is the same convention used throughout Dinamica EGO's table representation (see [[calculate_functors#connecting_data_inputs|Connecting Data Inputs]]). A key column can be Real or String, the same as any other column.
+  * Each column's type is inferred from its data, the same rule that applies to any table (see [[ego_script#constants|Constants]]): a numeric vector produces a Real column, a character vector produces a String column. R automatically converts string columns to **Factors** inside a ''data.frame'', and a Factor is neither of those — Dinamica requires plain **Character Vectors** to infer String correctly. Always build tables with ''stringsAsFactors = FALSE'' to prevent this conversion.
+For further detail on the underlying table representation, see [[external_communication#table|External Communication]].
-----
+==== Expression outputs ====
-===== Usage =====
+Values are returned to Dinamica by calling one of the following functions from the R script. Every call requires an identifier as its first parameter — the name Dinamica uses to place the value into the output struct — and the value itself, which can be constructed inline, as in the examples below, or supplied as a variable:
-The functor is available under the //Integration// tab at the library.
+^ Function ^ Output type ^ Notes ^ Example ^
+| ''outputDouble()'' | Real | Accepts any numeric value. | ''outputDouble("myDouble", 3.14)'' |
+| ''outputNumberVector()'' | Tuple | Accepts any collection of numbers. | ''outputNumberVector("myTuple", c(1:10))'' |
+| ''outputString()'' | String | Accepts any string value. | ''outputString("myString", "This is a string")'' |
+| ''outputLookupTable()'' | [[Lookup Table Type|Lookup Table]] | Requires two number vectors of equal length — one for the keys, one for the values. Lookup tables are always Real-typed on both sides; there is no String option. | ''outputLookupTable("myLUT", c(1:10), c(1:10) * 10)'' |
+| ''outputTable()'' | Table | Requires a table built with the [[https://www.r-tutor.com/r-introduction/data-frame|data.frame]] function, using ''stringsAsFactors = FALSE'' as described above. Its optional second parameter (default ''1'') sets how many leading columns, from the left, are key columns. | ''outputTable("myTable", data.frame(State = c("Massachusetts", "Massachusetts"), City = c("Boston", "Chelsea"), Population = c(667137, 39398), stringsAsFactors = FALSE), 2)'' |
-===== R Script Inputs =====
+==== Retrieving outputs ====
-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:
+''CalculateRExpression'' returns a single [[struct_type|Struct]] value (via its ''result'' output port) containing every value passed to an ''output*()'' function. To retrieve individual values from that struct, use the corresponding functor from the //Integration// group:
-  * [[Number Table]]
+^ Functor ^ Retrieves ^
+| [[Extract Struct Number]] | A value passed to ''outputDouble()'' |
+| [[Extract Struct Tuple]] | A value passed to ''outputNumberVector()'' |
+| [[Extract Struct String]] | A value passed to ''outputString()'' |
+| [[Extract Struct Lookup Table]] | A value passed to ''outputLookupTable()'' |
+| [[Extract Struct Table]] | A value passed to ''outputTable()'' |
-  * [[Number Value]]
+Each functor takes two inputs: the ''Struct'' returned by ''CalculateRExpression'', and the name of the entry to extract as a string constant.
-  * [[Number String]]
+==== Installing packages ====
-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:
+Packages are installed by calling ''dinamicaPackage("packageName")'' from within the expression — one call per package. Unlike [[calculate_python_expression|Calculate Python Expression]], there is no separate input port for listing packages; ''dinamicaPackage()'' is the only mechanism available.
-<code rsplus>
+''dinamicaPackage("packageName")'' also acts as R's ''library()'' call: when the package name matches the name of the module to load, calling it both installs the package (if not already present) and loads it, in a single call.
-# Will store the 5th key from the passed Lookup Table in the variable 'testing'
-testing <- t1$Keys[ 5 ];
-# Store the second passed String.
+<code rsplus>
-secondString <- s2;
+dinamicaPackage("moments");
-# Store the 10th passed Value.
-tempNumber <- v10;
 </code>
-===== R Script Outputs =====
+==== Setup ====
-To output data back to Dinamica EGO, the user must call a set of functions designed for this functionality:
+There are two ways to run R scripts from ''CalculateRExpression'' — though only the local installation is available on Linux.
-^ Function name  ^ Output Data Type  ^ Usage Example  ^
+=== Dinamica EGO Enhancement Plugin ===
-| 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.
+Windows only. Download and install the [[plugins_4|Dinamica EGO Enhancement Plugin]]. It contains everything needed to run R scripts inside Dinamica EGO, with no further configuration.
-<note important>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).</note>
+=== Local R installation ===
-Keep in mind:
+On Linux, this is the only option — Dinamica EGO always uses the R installation already present on the system. On Windows, it can be used as an alternative to the plugin. Either way, it requires:
-  * You can pass any kind of numeric value on the ''outputDouble'' function.
+  * R installed on the machine, with the ''Rscript'' executable (''Rscript.exe'' on Windows) present in its ''bin'' sub-folder.
+  * The [[external_communication|Dinamica package]] for R installed and at its latest version.
-  * Collections of numbers are valid number vector's.
+On Windows, this alternative installation is selected in the Dinamica EGO GUI by going to //Tools// → //Options// → //Integration// tab and enabling //Use alternative R installation for Calculate R Expression//.
-  * A [[Lookup Table Type|Lookup Table]] requires //2// number vectors, one for the "Keys" and another for the "Values". Both vectors must have the same number of elements.
+==== Examples ====
-  * The ''outputTable'' function requires a table, that can be construct with data.frame R function. Tt has an optional parameter too, to put how many Key columns the table has, from the leftmost column, the default value of it is 1.
+The following examples use a consistent set of inputs:
-<note important>Notice the use of the stringAsFactors = FALSE flag. This flag prevents R from converting the passed strings to Factors(numbers).</note>
-==== Tables / Lookup Tables ====
+  * ''t1'' — a lookup table of land cover patches, mapping ''Key'' (patch identifier) to ''Value'' (patch area)
+  * ''v1'' — a scalar minimum area threshold
+  * ''s1'' — a string giving the name to use for the threshold flag column
-[[Table Type|Tables]] or [[Lookup Table Type|Lookup Tables]] can be transferred to R using the [[Number Table]] functor. When dealing with each of these types extra caution must be taken:
+Compute the mean and total area across all patches, and report progress to the Message Log:
-=== Lookup Tables ===
+<code rsplus>
+patchMean <- mean(t1$Value);
+patchTotal <- sum(t1$Value);
+print(paste("Processed", length(t1$Value), "patches"));
-Lookup Tables are transferred to R as a List with two columns, "Keys" and "Values".
+outputDouble("meanArea", patchMean);
+outputDouble("totalArea", patchTotal);
+</code>
-Each column can be individually accessed by using the ''$'' operator, for example:
+> **Note:** The ''print()'' call is visible in Dinamica EGO's Message Log, shown as a Result-level message. Log levels are ordered Unconditional, Error, Warning, Result, Info, Info2, Debug, Debug2 — messages printed from R are only shown when the Message Log level is set to Result or a more verbose level; at Unconditional, Error, or Warning they are suppressed.
-  * ''t1$Keys[ 1 ]'' will access the first key of the Lookup Table ''t1''.
+Filter the lookup table down to patches whose area meets the threshold, and return the filtered lookup table:
-  * ''t2$Values[ 2 ]'' will access the second value of the Lookup Table ''t2''
-=== Tables ===
+<code rsplus>
+aboveThreshold <- t1$Value >= v1;
+filteredKeys <- t1$Key[aboveThreshold];
+filteredValues <- t1$Value[aboveThreshold];
-Tables are transferred to R as a [[https://en.wikibooks.org/wiki/R_Programming/Working_with_data_frames|DataFrame]] type variable. Each column can be individually accessed by using the ''$'' operator, just like Lookup Tables. Please check [[external_communication#table|this page]] for more information on how to deal with Tables. The rules for them in [[Calculate R Expression]] are the same as sending and receiving through [[External Communication]].
+outputLookupTable("filteredPatches", filteredKeys, filteredValues);
+</code>
-===== Example Scripts =====
-==== Multiply each value of the passed Lookup Table by itself ====
-{{ ::ex1_calculate_r.png?nolink |}}
+Build and return a table with one row per patch, including a column that flags whether each patch meets the threshold. The column's name is taken from the passed string ''s1'' rather than being hard-coded:
-Expression:
 <code rsplus>
-for ( i in 1:length( t1$Values ) ) {
+patchFlags <- data.frame(
-  tempValue <- t1$Values[ i ];
+    PatchId = t1$Key,
-  t1$Values[ i ] = tempValue * tempValue;
+    Area = t1$Value,
-}
+    MeetsThreshold = t1$Value >= v1,
+    stringsAsFactors = FALSE
+);
+names(patchFlags)[3] <- s1;
-outputLookupTable( "poweredTable", t1$Keys, t1$Values );
+outputTable("patchSummary", patchFlags, 1);
 </code>
-==== Extract the mean of passed Lookup Table values ====
+Install the ''moments'' package and use it to compute the skewness of the patch area distribution — a statistic not available in base R — then flag patches whose area is a statistical outlier:
-{{ ::ex2_calculate_r.png?nolink |}}
-Expression:
 <code rsplus>
-tableMean <- mean( t1$Values );
+dinamicaPackage("moments");
-print( paste( "Mean is", tableMean ) );
-outputDouble( "mean", tableMean );
+patchMean <- mean(t1$Value);
+patchStdDev <- sd(t1$Value);
+patchSkewness <- skewness(t1$Value);
+isOutlier <- abs(t1$Value - patchMean) > 2 * patchStdDev;
+outlierPatches <- data.frame(
+    PatchId = t1$Key[isOutlier],
+    Area = t1$Value[isOutlier],
+    stringsAsFactors = FALSE
+);
+outputDouble("meanArea", patchMean);
+outputDouble("stdDevArea", patchStdDev);
+outputDouble("skewnessArea", patchSkewness);
+outputTable("outlierPatches", outlierPatches, 1);
 </code>
-Noticed the ''print()'' statement? Dinamica EGO's Message Log will show output messages from the R script (as Result's).
+==== Writing the expression in EGO Script ====
-==== Plot passed Lookup Table to an image on the path specified by passed String ====
+Like [[calculate_python_expression|Calculate Python Expression]], the ''Expression'' input is type [[ego_script#constants|Code]], which is represented in the underlying script using base64 encoding — impractical to write or edit directly as a text constant. Instead, connect a ''String'' carrier functor containing the R expression text to the ''Expression'' port; its output is accepted wherever a ''Code'' value is expected. Since only this one output is needed, the carrier can be [[ego_script#inline_syntax|inlined]] directly into the call.
-{{ ::ex3_calculate_r.png?nolink |}}
+This limitation is specific to hand-written EGO Script. In the Dinamica EGO GUI, the ''Expression'' port has a dedicated code editor that edits the ''Code'' value directly — the ''String'' carrier workaround is only necessary when writing or editing the ''.ego'' file as text.
-Expression:
+<code>
-<code rsplus>
+result := CalculateRExpression (String $"(
-outputFile  <- s1;
+aboveThreshold <- t1$Value >= v1;
-print( paste( "Plotting to", outputFile ) );
+outputLookupTable("filteredPatches", t1$Key[aboveThreshold], t1$Value[aboveThreshold]);
-jpeg( outputFile, quality=100 );
+)") .no {{
-plot( t1 );
+    NumberTable landCoverAreas 1;
-dev.off();
+    NumberValue minimumArea    1;
+}};
+filteredPatches := ExtractStructLookupTable result "filteredPatches";
 </code>
+===== Group =====
+[[Functor List#Integration|Integration]]
 ===== Internal Name =====
 CalculateRExpression