如何在Jupyter中从Python内核切换至R内核？解决R Markdown转ipynb后无法切换内核的问题

It sounds like your Jupyter setup either lacks a properly registered R kernel, or the converted notebook isn't configured to use it. Let's walk through the most effective fixes step by step:

1. Install and Register the R Kernel with Jupyter #

Even if you have an R environment set up, Jupyter won't recognize it until you register the R kernel. Here's how to do that:

• Open your R console (or RStudio)
• Install the IRkernel package, which connects R to Jupyter:

  install.packages("IRkernel")
  

• Register the kernel so Jupyter can see it:

  IRkernel::installspec()
  

  If you want this kernel available to all users on your system, add user = FALSE:

  IRkernel::installspec(user = FALSE)
  

Restart Jupyter after this, and you should see an "R" option in the kernel dropdown menu when you open your notebook.

2. Manually Set the Kernel in Your Existing Notebook #

If the kernel still doesn't show up, or you want to force the notebook to use R by default, edit the notebook's metadata directly:

• Open script.ipynb in a text editor (VS Code, nano, Sublime Text, etc.)
• Look for the "kernelspec" section near the top of the file—it probably looks like this:

  "kernelspec": {
    "display_name": "Python 3",
    "language": "python",
    "name": "python3"
  }
  

• Replace it with the R kernel configuration (the name is usually ir, but adjust if yours differs):

  "kernelspec": {
    "display_name": "R",
    "language": "r",
    "name": "ir"
  }
  

• Save the file and reopen it in Jupyter—it should now load the R kernel automatically.

3. Alternative: Use rpy2 for Mixed Python/R Workflows #

If you need to run R code within a Python notebook (instead of switching kernels entirely), fix the ModuleNotFoundError for rpy2:

• Install rpy2 in your Python environment using pip:

  pip install rpy2
  

  Note: You may need system dependencies first. For Ubuntu/Debian:

  sudo apt-get install r-base python3-dev libxml2-dev libcurl4-openssl-dev libssl-dev
  

  For macOS (using Homebrew):

  brew install r python
  

• Once installed, load the rpy2 extension in your notebook:

  %load_ext rpy2.ipython
  

• Now you can use the %%R cell magic to run R code in dedicated cells:

  %%R
  # Example R code
  data <- c(10, 20, 30)
  print(mean(data))
  

4. Avoid the Issue Next Time: Convert with Kernel Specified #

When using jupytext to convert your R Markdown file to ipynb, specify the R kernel upfront to skip manual configuration:

jupytext --to notebook --set-kernel ir script.Rmd

This will generate an ipynb file that uses the R kernel by default.

Content of the question comes from Stack Exchange, asked by Lerner Zhang