Introduction

In today’s post we are going to go over VBA code to check if a sheet exists and then we are going to call that function from R using the RDCOMClient package. This can be useful when you need to perform certain actions based on the existence of a sheet in an Excel workbook.

Let’s break this down step by step. We’ll start by writing a VBA function to check if a sheet exists, then we’ll show how to call this function from R using the RDCOMClient package.

Code and Examples

VBA Code to Check if a Sheet Exists

VBA Function

First, let’s create a simple VBA function to check if a sheet exists in the workbook.

Function SheetExists(sheetName As String) As Boolean
    Dim ws As Worksheet
    SheetExists = False
    For Each ws In ThisWorkbook.Sheets
        If ws.Name = sheetName Then
            SheetExists = True
            Exit Function
        End If
    Next ws
End Function

Let’s see it in action:

Explanation:

• Function SheetExists(sheetName As String) As Boolean: Defines a function named SheetExists that takes a sheet name as a string and returns a boolean.
• Dim ws As Worksheet: Declares a variable ws as a worksheet.
• SheetExists = False: Initializes the function to return False by default.
• For Each ws In ThisWorkbook.Sheets: Loops through each worksheet in the workbook.
• If ws.Name = sheetName Then: Checks if the current worksheet’s name matches the provided sheet name.
• SheetExists = True: Sets the function to return True if a match is found.
• Exit Function: Exits the function as soon as a match is found.
• Next ws: Continues to the next worksheet.

This VBA function SheetExists takes a sheet name as an argument and returns True if the sheet exists, and False otherwise.

R Code to Execute the VBA Macro and Return a Boolean Value

To run this VBA macro from R, you can use the RDCOMClient package. Here’s how you can do it:

1. First, you’ll need to create an Excel workbook with the VBA macro.
2. Then, use the following R code to execute the macro.

R Code using RDCOMClient to Execute the VBA Macro

First you need to install the package which can be slightly cumbersome:

# Install RDCOMClient if not already installed
if (!requireNamespace("RDCOMClient", quietly = TRUE)) {
  install.packages("RDCOMClient", repos = "http://www.omegahat.net/R")
}

# Load RDCOMClient package
library(RDCOMClient)

# Create a connection to Excel
excel_app <- COMCreate("Excel.Application")

# Open your workbook
wb_path <- "C:/Users/ssanders/Documents/GitHub/steveondata/posts/2024-06-12/sheet_exists.xlsm"
workbook <- excel_app$Workbooks()$Open(wb_path)

# Ensure Excel is visible (optional)
excel_app[["Visible"]] <- TRUE

# Run the VBA function and get the result
sheet_name <- "Sheet1" # Replace with the sheet name you want to check
result <- excel_app$Run("SheetExists", sheet_name)

# Close the workbook without saving
workbook$Close(FALSE)

[1] TRUE

# Quit the Excel application
excel_app$Quit()

NULL

# Release the COM objects
rm(excel_app, workbook)

# Output the result
result

[1] TRUE

Replace wb_path with the actual path to your Excel file containing the VBA macro.

Explanation:

• RDCOMClient::COMCreate(“Excel.Application”): Creates a COM object for Excel.
• excel_app[[“Visible”]] <- TRUE: Makes Excel visible (optional, can be removed).
• excel_app[[“Workbooks”]]$Open(“C:\path\to\your\workbook.xlsx”): Opens the specified workbook. Adjust the path as needed.
• excel_app$Run(“SheetExists”, sheet_name): Runs the SheetExists VBA function with the provided sheet name and stores the result.
• workbook$Close(FALSE): Closes the workbook without saving changes.
• excel_app$Quit(): Quits the Excel application.
• excel_app <- NULL: Releases the COM object resources.

R Code using RDCOMClient to Achieve the Same Goal Without VBA

If you prefer to check if a sheet exists directly using R without invoking VBA, you can do it with the RDCOMClient package as well:

# Load RDCOMClient package
library(RDCOMClient)

# Create a connection to Excel
excel_app <- COMCreate("Excel.Application")

# Open your workbook
wb_path <- "C:/Users/ssanders/Documents/GitHub/steveondata/posts/2024-06-12/sheet_exists.xlsm"
workbook <- excel_app$Workbooks()$Open(wb_path)

# Ensure Excel is visible (optional)
excel_app[["Visible"]] <- TRUE

# Function to check if a sheet exists
sheet_exists <- function(workbook, sheet_name) {
  sheets <- workbook$Sheets()
  for (i in 1:sheets$Count()) {
    if (sheets$Item(i)$Name() == sheet_name) {
      return(TRUE)
    }
  }
  return(FALSE)
}

# Check if the sheet exists
sheet_name <- "Sheet1" # Replace with the sheet name you want to check
result <- sheet_exists(workbook, sheet_name)

# Close the workbook without saving
workbook$Close(FALSE)

[1] TRUE

# Quit the Excel application
excel_app$Quit()

NULL

# Release the COM objects
rm(excel_app, workbook)

# Output the result
result

[1] TRUE

In this code, we directly check the existence of a sheet using the RDCOMClient package without invoking a VBA macro.

Explanation:

• Similar steps to the previous R code, but instead of running a VBA macro, it directly interacts with the Excel object model.
• Loops through the sheets in the workbook to check if the specified sheet exists.

Summary

• The VBA code checks if a sheet exists in an Excel workbook.
• The first R code executes the VBA macro using the RDCOMClient package.
• The second R code achieves the same goal directly using the RDCOMClient package without invoking VBA.

I encourage you to try these code snippets on your own to get hands-on experience. Experiment with different sheet names and see how the functions behave. Understanding how to automate tasks with VBA and R can greatly enhance your productivity and open up new possibilities for your data analysis workflows.

Bonus

As an added bonus I have included the VBA Enabled Excel file that contains the VBA code to check if a sheet exists. You can download the file from the link below:

Workbook Here!

Happy coding!