This post should have been written in 2024, but my hands were full at that time. I sadly learned from the obituary of Fritz Leisch on the R Project website that he passed away in April 2024.

I didn’t have much direct contact with Fritz, but my career in R would have been very different without his pioneering work on Sweave, which was the main inspiration for me to create knitr later. I used Sweave extensively from 2008 to 2011. It was amazing to me that such a small piece of software could be a game changer in data analysis workflows and reproducible research in general—topics to which not enough people had paid attention.

One of my long-standing regrets was item #4 in my list of mistakes. As an arrogant young man, I was not humble or grateful in the early days. I wrote him a thank-you note in 2020:

From: Yihui Xie <x***[email protected]>
Date: Wed, Nov 25, 2020 at 11:12 PM
Subject: Thank you for creating Sweave!
To: Friedrich Leisch <F***[email protected]>

Hi Fritz,

It’s Thanksgiving Day here in the US, and I happen to be thinking of you lately. I don’t think I’ve ever thanked you personally for Sweave, which opened a door to my PhD research and later to a job career almost ten years ago. This is definitely a late thank-you note, but better late than never!

I’ve been reflecting on my past decade recently, and I realized that I was very unfair to Sweave in the beginning when creating and promoting the knitr package. There was no way I could have created knitr without your invention of Sweave in the first place. I really want to apologize for the silly and arrogant comments that I made about Sweave in the early days. In retrospect, those comments were rather unfair and seriously lacked appreciation for your work. I wish they didn’t hurt you too much. My sincere apologies if they did!

Hope all is well with you in this difficult time!

Regards,
Yihui

I didn’t receive a reply, but I’ve learned “C’est la vie” over the years.

Jürgen Symanzik and co-authors published a memorial for Fritz in Computational Statistics in late 2024, which included a photo of Fritz, Jürgen, and me in Fig. 2. We were attending a data visualization workshop in Bremen, Germany in 2008. It was my first international trip, and I got to know many experts in the field, including Fritz, Jürgen, Michael Friendly, Lee Wilkinson, Nathan Yau, Antony Unwin, Simon Urbanek, and the GGobi team (Andreas Buja, Debby Swayne, Di Cook, Heike Hofmann, Hadley Wickham, and Michael Lawrence).

Oh, too many memories, and I’m becoming nostalgic. I remember sitting next to Lee and chatting with him on the bus back from the group dinner. Sadly, he has also passed away (in 2021). I happen to be exploring the grammar of graphics recently.

For those interested in learning more about Fritz, The R Journal also published a memorial in 2024. He will surely be missed and remembered by many people, including myself.