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General Issue: Investigate the topic of metadata for pdf in R #15
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Background Information
We want to investigate whether we can, with low cost and minimal dependencies, provide metadata support for our PDFs. All cells are saved as pdf metadata.
A hack with a title as a JSON
library(jsonlite)
# 1. Create a list of your custom metadata
my_metadata <- list(
title = "Alpha",
header1 = 42,
status = "Draft",
tags = c("R", "Plot", "JSON")
)
# 2. Convert to a JSON string - we should use base R for that - we control what we convert
json_string <- toJSON(my_metadata, auto_unbox = TRUE)
# 3. Pass the JSON string to the title argument
pdf("json_metadata_plot.png", title = json_string)
plot(1:10, main = "Data Visualization")
dev.off()
Using a system library
https://stackoverflow.com/a/24254259/5442527
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jimrothstein commentedon Feb 28, 2026
@Polkas
Have not worked with
ExifTool. Done other things in pharmaverse; this seems interesting and would like to try.jim
Polkas commentedon Feb 28, 2026
Hey @jimrothstein, it is fantastic that you want to contribute.
This is a really interesting task, and we have at least a few options for how to approach it:
Vignette Example: Check if we can add an example to a vignette demonstrating how to integrate this into a workflow (e.g., using the xmpdf R package).
Internal Solution: Consider building a lightweight, internal solution directly within gridify.
Advanced: We could also consider reporting it to the CRAN community, the lack of this specific grDevices::pdf capability and even try to contribute to base R itself. Since the R pdf() device already adds metadata like the title and author, I assume there is existing code we could easily extend.
Please assign yourself to the issue once you have decided to move forward with the contribution.
jimrothstein commentedon Feb 28, 2026
@Polkas
Hi - Let me aim for simple, first. I don't have write access and so will fork.
Working through gridify and exiftool ... all installed.
jimrothstein commentedon Mar 5, 2026
@Polkas
Still playing ... time to study packages you have already referenced.
gridify_mtcars.pdf
Polkas commentedon Mar 5, 2026
Thank you for working on that.
No pressure, even trying to help is a fantastic contribution.
FYI. We can catch up to discuss it or I can propose another interesting issue in future.
BTW. The first empty page is a known issue.
As I remeber you need to use pdf(..., onefile = TRUE) and/or print() for image.
jimrothstein commentedon Mar 30, 2026
@Polkas
Got sidetracked, but did read a bit re: grid/grobs ( nice intro: https://bookdown.org/rdpeng/RProgDA/the-grid-package.html) and poked about some of other tools.
About to work through ( r-xmpdf https://github.com/trevorld/r-xmpdf?tab=readme-ov-file#overview)
I am learning, but don't have clear picture, yet, of vignette idea you mentioned. Should I go all the way back to Adobe's XMP (https://opensource.adobe.com/dc-acrobat-sdk-docs/library/pdfmark/pdfmark_Syntax.html) ??
Suggestion: I'll try to rough sketch what vignette might include. (in 1 week). Then you add/subtract to it?
Thx
Polkas commentedon May 21, 2026
we have an active PR for it now. We decided to apply sidecar file solution. Feel free to comment on it:) By default no metadata is saved.
#19