Troubleshooting Custom Packages in Shiny Apps: A Step-by-Step Guide

Introduction to R Packages and Shiny Apps

In this article, we’ll delve into the world of R packages and Shiny apps. Specifically, we’ll explore how to load an own package in a Shiny app using R. We’ll also address the common issue of uploading a Shiny app with a custom package to shinyapps.io.

What are R Packages?

In R, a package is a collection of functions, datasets, and other resources that can be shared and reused across multiple projects. Packages provide a convenient way to organize and manage code, making it easier to maintain large projects. R packages typically have a DESCRIPTION file that contains metadata about the package, such as its name, version, and dependencies.

What is a Shiny App?

A Shiny app is an interactive web application built using R’s Shiny framework. Shiny apps allow users to create engaging and dynamic interfaces for data visualization, machine learning, or other applications. These apps can be run locally on a user’s computer or deployed online through services like shinyapps.io.

The Problem: Loading a Custom Package in Shiny App

The problem at hand is that when we try to load an own package in a Shiny app using library(NxT), it fails with an error message indicating that the package does not appear to be an R package (no DESCRIPTION file). However, on our local machine, the package works fine.

Solution: Understanding the Role of DESCRIPTION Files

The DESCRIPTION file plays a crucial role in defining an R package. It contains metadata about the package, such as its name, version, and dependencies. When we try to load a package using library(), R looks for a corresponding DESCRIPTION file in the package’s directory.

In our case, the problem lies in the fact that shinyapps.io is not able to find the DESCRIPTION file of our custom package. This is because the package is not properly installed on CRAN (the Comprehensive R Archive Network), which is the central repository for R packages.

Step 1: Verify the Package’s Installation on CRAN

To verify whether our custom package is installed on CRAN, we can use the devtools::install_github() function with the check_for_cran parameter set to TRUE. This will check if the package has a valid DESCRIPTION file and install it on CRAN if necessary.

# Install the package on CRAN (if not already installed)
devtools::install_github("zertupo/NxT", check_for_cran = TRUE)

Step 2: Update the Package’s Dependencies

It is possible that our custom package depends on other packages that are not properly installed. We can use devtools::install() to install all dependencies required by our package.

# Install all dependencies of the package
devtools::install("zertupo/NxT")

Step 3: Check for Incompatible Functions

In some cases, it may be due to incompatible functions between Shiny app and our custom package. We can try to check if any functions in our custom package are not compatible with Shiny.

# Load the package in R Studio's console
library(NxT)
# Try calling a function that is known to work
NxT::my_function()

If this fails, it may be an indication of an incompatible function between the two packages.

Step 4: Use the `devtools::install_github()` Function with a Specific Version

Sometimes, an outdated version of our custom package might be causing issues. We can try installing a specific version using devtools::install_github() with the build_version parameter set to TRUE.

# Install a specific version of the package
devtools::install_github("zertupo/NxT", build_version = TRUE)

Step 5: Check the Shiny App’s Dependencies

It is also possible that our custom package depends on packages that are not properly installed in the Shiny app. We can try installing all dependencies required by our Shiny app using install.packages().

# Install all dependencies of the Shiny app
install.packages("dplyr", "tidyverse")

Conclusion

Loading a custom package in a Shiny app requires attention to detail and careful troubleshooting. By verifying the package’s installation on CRAN, updating its dependencies, checking for incompatible functions, using specific versions, and ensuring all dependencies are installed, we can resolve common issues that prevent our packages from working correctly.

In conclusion, this article has provided a comprehensive guide to loading custom packages in Shiny apps. We have explored the role of DESCRIPTION files, installing packages on CRAN, updating dependencies, checking for incompatible functions, using specific versions, and ensuring all dependencies are installed. By following these steps, you can successfully load your own package in a Shiny app.

Additional Tips and Tricks

Always verify that your custom package has a valid DESCRIPTION file.
Ensure that all dependencies required by your custom package are properly installed.
Check for incompatible functions between your custom package and the Shiny app.
Use specific versions of your custom package to resolve version conflicts.
Install all dependencies required by your Shiny app using install.packages().
Consider creating a Makefile in your project directory to automate tasks such as building and deploying your app.

By following these tips, you can further improve the reliability and stability of your custom packages in Shiny apps.

Last modified on 2023-08-29