Getting Error on Missing PNG when trying to generate a PDF

[bshor]

Hello,

I'm running the latest versions of R and Rstudio on Arch-derived Garuda Linux. I'm also running the latest version of Google Chrome.

I want to output PDF from my Xaringen slides (I can see the HTML just fine).

But I get the following error on a specific slide.

> xaringanBuilder::build_pdf("Presentations/USC2021/statepolarization_2021.Rmd")
✓ Building Presentations/USC2021/statepolarization_2021.Rmd into Presentations/USC2021/statepolarization_2021.html ... done
x Building Presentations/USC2021/statepolarization_2021.html into Presentations/USC2021/statepolarization_2021.pdf ... failed
Error in force(expr) : 
  Failed to generate output. Reason: Failed to open http://127.0.0.1:7799/Plots/Legislatures_2021/States/legislatures_party_density.png (HTTP status code: 404)

It seems like it is trying to open a file on a web server? Why? I have the plot in my file system.

I can see the presentation perfectly in the Moon Reader and when I open the html presentation in Chrome.

Interestingly, when I try to print the presentation from Chrome itself, it is missing several plots, including the one that xaringanBuilder complains about. Here's the screenshot of what I mean. Notice that the PDF preview is missing that plot, when the underlying HTML display in Chrome looks fine.

[gadenbuie]

Can you share the source code for that slide?

[jhelvy]

I've had some issues in the past with images that go beyond the page margins, not sure if that is the source of the issue here though as it doesn't typically throw an error.

[bshor]

Can you share the source code for that slide?

Sure. The presentation references plots I pre-generated in R. The first slide doesn't generate an error:

# Change in Ideal Points Distributions

```{r echo=FALSE, out.width="50%", fig.align='center'}
knitr::include_graphics("../../Plots/Legislatures_2021/States/legislatures_year_party_density.png")

But the second one does, and has the funny behavior I pointed out above: it is blank when printed.

1996 and 2020

knitr::include_graphics("../../Plots/Legislatures_2021/States/legislatures_party_density.png")

[bshor]

I've had some issues in the past with images that go beyond the page margins, not sure if that is the source of the issue here though as it doesn't typically throw an error.

Interesting. The slide that gives me a problem is expanded to 85% instead of 50%. But it doesn't go beyond the page margins in the Moon Reader previewer:

I tried reducing the out.width, but that didn't solve the PDF creation issue.

[gadenbuie]

The problem is that the plot you've created isn't in the same directory as your slides. This is one of the ways that xaringan is somewhat different from other R Markdown outputs — the default target of xaringan slides are the web, where you'd need to copy all the files onto a web server, so everything needs to be contained in the same folder.

There is a work around, however. You can add self_contained: true to the YAML header of your slides under the moon_reader output.

OR you can use xaringanBuilder to render your slides to HTML first with build_html(), setting self_contained = TRUE in that call

library(xaringanBuilder)
build_html("Presentations/USC2021/statepolarization_2021.Rmd", self_contained = TRUE)

and then calling build_pdf() on the HTML file

build_pdf("Presentations/USC2021/statepolarization_2021.html")

Here's a small reprex that demonstrates the issue. Put the following in slides/issue-40.Rmd (i.e. issue-40.Rmd in a slides/ directory)

---
output:
  xaringan::moon_reader:
    seal: false
---

This slide makes a plot **in the parent directory** and then includes the image.

```{r plot, results="hide"}
png("../plot.png", width = 8, height = 4, units = "in", res = 150)
hist(faithful$waiting)
dev.off()

Then move into the directory and try to build the PDF file:

build_pdf("issue-40.Rmd") [WARNING] This document format requires a nonempty