Opening an Excel Workbook with VBA and Calling it from R

code
rtip
vba
Author

Steven P. Sanderson II, MPH

Published

August 14, 2024

Introduction

In this post, we’ll cover how to open an Excel workbook using VBA and then call this VBA code from R. This guide will help you automate tasks in Excel directly from R, combining the strengths of both tools. We’ll break down the VBA code and the R script step by step to make the process clear and easy to follow.

Step 1: Writing the VBA Code

First, let’s create the VBA code that will open an Excel workbook. VBA, or Visual Basic for Applications, is a programming language integrated into Excel, allowing for automation of repetitive tasks. Below is a simple VBA script to open a workbook from a specified path:

Sub OpenWorkbook()
    Dim workbookPath As String
    Dim workbook As Workbook
    
    ' Specify the path to your workbook
    workbookPath = "C:\Path\To\Your\Workbook.xlsx"
    
    ' Open the workbook
    Set workbook = Workbooks.Open(workbookPath)
    
    ' Optional: Make the workbook visible
    workbook.Application.Visible = True
End Sub

Explanation:

  • Dim workbookPath As String: This line declares a variable named workbookPath to store the file path of the workbook.
  • Dim workbook As Workbook: This declares a variable workbook that will hold the workbook object after it’s opened.
  • workbookPath = “C:.xlsx”: Replace the placeholder path with the actual path to your Excel file.
  • Set workbook = Workbooks.Open(workbookPath): This line opens the workbook and assigns it to the workbook variable.
  • workbook.Application.Visible = True: This optional line makes the Excel application visible after opening the workbook.

Step 2: Testing the VBA Code

Before proceeding to the R script, it’s important to test the VBA code directly in Excel to ensure it works correctly.

  1. Open Excel and press ALT + F11 to access the VBA editor.
  2. Insert a new module by clicking Insert > Module.
  3. Copy and paste the above VBA code into the module.
  4. Run the OpenWorkbook macro by pressing F5 or by selecting Run > Run Sub/UserForm.

If the workbook opens successfully, you’re ready to move on to integrating this with R.

Step 3: Calling the VBA Code from R

Now that we have the VBA macro ready, let’s call it from R using the RDCOMClient package. The following R code will initialize Excel, run the VBA macro to open the workbook, and then optionally close Excel.

library(RDCOMClient)

# Initialize the COM object for Excel
excelApp <- COMCreate("Excel.Application")

# Open the Excel workbook
fn <- "C:\\Path\\To\\Your\\Workbook.xlsx"
xlWbk <- excelApp$Workbooks()$Open(fn)

# Make Excel visible (optional)
excelApp[["Visible"]] <- TRUE

# Optional: Close Excel after running the script
excelApp$Quit()

Explanation:

  • library(RDCOMClient): This loads the RDCOMClient package, enabling R to interact with Excel via COM (Component Object Model).
  • COMCreate(“Excel.Application”): This line creates a COM object representing the Excel application, which allows R to control Excel.
  • fn <- “C:\Path\To\Your\Workbook.xlsx”: Replace this with the actual path to your Excel file. Note that double backslashes (\\) are required to correctly format the path in R.
  • xlWbk <- excelApp\(Workbooks()\)Open(fn): This line opens the specified Excel workbook using the path stored in fn.
  • excelApp[[“Visible”]] <- TRUE: This optional line makes the Excel application visible, allowing you to see the workbook open.
  • excelApp$Quit(): This line closes Excel after the script runs. If you prefer to keep Excel open, you can omit or comment out this line.

Step 4: Running the R Script

Once the R script is ready, you can run it in your R environment to open the workbook using the VBA macro. This integration between R and Excel is powerful for automating tasks, especially when you need to handle Excel files programmatically.

Your Turn!

This guide gives you a solid foundation to start automating Excel tasks using R and VBA. I encourage you to experiment with the code provided and adapt it to your specific needs. For example, you could expand the VBA macro to perform additional actions, such as manipulating data in the workbook, or explore other functionalities of the RDCOMClient package to further enhance your workflows.

By experimenting with these tools, you’ll gain greater control over your Excel automation tasks and streamline your work processes. If you encounter any issues, reviewing the code or referring to relevant documentation can help you overcome them.

Happy coding!