Tutorial: Create an R-powered Power BI visual

• 05/11/2020
• 4 minutes to read
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This tutorial describes how to create an R-powered visual for Power BI.

In this tutorial, you learn how to:

Prerequisites

• A Power BI Pro account. Sign up for a free trial before you begin.
• The R engine. You can download it free from many locations, including the Revolution Open download page and the CRAN Repository. For more information, see Create Power BI visuals using R.
• Power BI Desktop.
• Windows PowerShell version 4 or later for Windows users OR the Terminal for OSX users.

Getting started

1. Prepare sample data for the visual. You can save these values to an Excel database or .csv file and import it into Power BI Desktop.

   MonthNo	Total Units
   1	2303
   2	2319
   3	1732
   4	1615
   5	1427
   6	2253
   7	1147
   8	1515
   9	2516
   10	3131
   11	3170
   12	2762

2. To create a visual, open PowerShell or Terminal, and run the following command:

   pbiviz new rVisualSample -t rvisual
   

   This command creates a new folder structure based on the rvisual template. This template includes a basic, ready-to-run R-powered visual that runs the following R script:

   plot(Values)
   

   The Values data frame will contain columns in Values data role.

3. Assign data to the developer visual by adding MonthNo and Total units to Values for the visual.

   

Editing the R Script

When you use pbiviz to create the R-powered visual based on the rvisual template, it creates a file called script.r in the root folder of the visual. This file holds the R script that runs to generate the image for a user. You can create your R script in Power BI Desktop.

1. In Power BI Desktop, select R script visual:

   

2. Paste this R code into the R script editor:

   x <- dataset[,1] # get the first column from dataset
   y <- dataset[,2] # get the second column from dataset
   
   columnNames = colnames(dataset) # get column names
   
   plot(x, y, type="n", xlab=columnNames[1], ylab=columnNames[2]) # draw empty plot with axis and labels only
   lines(x, y, col="green") # draw line plot
   

3. Select the Run script icon to see the result.

   

4. When your R script is ready, copy it to the script.r file in your visual project created at one of the previous steps.

5. Change the name of dataRoles in capabilities.json to dataRoles. Power BI passes data as the dataset data frame object for the R script visual, but the R visual gets the data frame name according to dataRoles names.

   {
     "dataRoles": [
       {
         "displayName": "Values",
         "kind": "GroupingOrMeasure",
         "name": "dataRoles"
       }
     ],
     "dataViewMappings": [
       {
         "scriptResult": {
           "dataInput": {
             "table": {
               "rows": {
                 "select": [
                   {
                     "for": {
                       "in": "dataset"
                     }
                   }
                 ],
                 "dataReductionAlgorithm": {
                   "top": {}
                 }
               }
             }
           },
           ...
         }
       }
     ],
   }
   

6. Add the following code to support resizing the image in the src/visual.ts file.

     public onResizing(finalViewport: IViewport): void {
         this.imageDiv.style.height = finalViewport.height + "px";
         this.imageDiv.style.width = finalViewport.width + "px";
         this.imageElement.style.height = finalViewport.height + "px";
         this.imageElement.style.width = finalViewport.width + "px";
     }
   

Add libraries to visual package

This procedure allows your visual to use the corrplot package.

1. Add the library dependency for your visual to dependencies.json. Here is an example of the file content:

   {
     "cranPackages": [
       {
         "name": "corrplot",
         "displayName": "corrplot",
         "url": "https://cran.r-project.org/web/packages/corrplot/"
       }
     ]
   }
   

   The corrplot package is a graphical display of a correlation matrix. For more information about corrplot, see An Introduction to corrplot Package.

2. After you make these changes, start using the package in your script.r file.

   library(corrplot)
   corr <- cor(dataset)
   corrplot(corr, method="circle", order = "hclust")
   

The result of using corrplot package looks like this example:

Adding a static property to the property pane

Enable users to change UI settings. To do this, add properties to the property pane that change the user-input based behavior of the R script.

You can configure corrplot by using the method argument for the corrplot function. The default script uses a circle. Modify your visual to let the user choose between several options.

1. Define the object and property in the capabilities.json file. Then use this object name in the enumeration method to get those values from the property pane.

   {
     "settings": {
     "displayName": "Visual Settings",
     "description": "Settings to control the look and feel of the visual",
     "properties": {
       "method": {
         "displayName": "Data Look",
         "description": "Control the look and feel of the data points in the visual",
         "type": {
           "enumeration": [
             {
               "displayName": "Circle",
               "value": "circle"
             },
             {
               "displayName": "Square",
               "value": "square"
             },
             {
               "displayName": "Ellipse",
               "value": "ellipse"
             },
             {
               "displayName": "Number",
               "value": "number"
             },
             {
               "displayName": "Shade",
               "value": "shade"
             },
             {
               "displayName": "Color",
               "value": "color"
             },
             {
               "displayName": "Pie",
               "value": "pie"
             }
           ]
         }
       }
     }
   }
   

2. Open the src/settings.ts file. Create a CorrPlotSettings class with the public property method. The type is string and the default value is circle. Add the settings property to the VisualSettings class with the default value:

   "use strict";
   
   import { dataViewObjectsParser } from "powerbi-visuals-utils-dataviewutils";
   import DataViewObjectsParser = dataViewObjectsParser.DataViewObjectsParser;
   
   export class VisualSettings extends DataViewObjectsParser {
     public rcv_script: rcv_scriptSettings = new rcv_scriptSettings();
     public settings: CorrPlotSettings = new CorrPlotSettings();
   }
   
   export class CorrPlotSettings {
     public method: string = "circle";
   }
   
   export class rcv_scriptSettings {
     public provider;
     public source;
   }
   

   After these steps, you can change the property of the visual.

   

   Finally, the R script must start with a property. If the user doesn't change the property, the visual doesn't get any value for this property.

   For R runtime variables for the properties, the naming convention is <objectname>_<propertyname>, in this case, settings_method.

3. Change the R script in your visual to match the following code:

   library(corrplot)
   corr <- cor(dataset)
   
   if (!exists("settings_method"))
   {
       settings_method = "circle";
   }
   
   corrplot(corr, method=settings_method, order = "hclust")
   

Your final visual looks like the following example:

Next steps

To learn more about R-powered visuals, see Use R-powered Power BI visuals in Power BI.

For more information about R-powered visuals in Power BI Desktop, see Create Power BI visuals using R.