the PNG device produces... pdf files

[joelgombin]

I try to knit this .Rmd file:

---
title: "test"
date: "19/07/2019"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE, fig.path = "./figures_test/", dev = ragg::agg_png())
```

## R Markdown

This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:

```{r cars}
summary(cars)
```

## Including Plots

You can also embed plots, for example:

```{r pressure}
plot(pressure)
```

But the plot files generated are... pdf file. And if I try to force the fig.ext knitr parameter, I get (as I should) PDFs with png extensions.

And here is the output of devtools::session_info():

─ Session info ─────────────────────────────────────────────────────────────────────────────────────────────────────────────
 setting  value                       
 version  R version 3.6.0 (2019-04-26)
 os       Ubuntu 18.04.2 LTS          
 system   x86_64, linux-gnu           
 ui       RStudio                     
 language (EN)                        
 collate  fr_FR.UTF-8                 
 ctype    fr_FR.UTF-8                 
 tz       Europe/Paris                
 date     2019-07-19                  

─ Packages ─────────────────────────────────────────────────────────────────────────────────────────────────────────────────
 package     * version date       lib source        
 assertthat    0.2.1   2019-03-21 [3] CRAN (R 3.5.3)
 backports     1.1.4   2019-04-10 [3] CRAN (R 3.5.3)
 callr         3.2.0   2019-03-15 [3] CRAN (R 3.5.3)
 cli           1.1.0   2019-03-19 [3] CRAN (R 3.5.3)
 crayon        1.3.4   2017-09-16 [3] CRAN (R 3.5.0)
 desc          1.2.0   2018-05-01 [3] CRAN (R 3.5.0)
 devtools      2.0.2   2019-04-08 [3] CRAN (R 3.5.3)
 digest        0.6.19  2019-05-20 [3] CRAN (R 3.6.0)
 evaluate      0.14    2019-05-28 [3] CRAN (R 3.6.0)
 fs            1.3.1   2019-05-06 [3] CRAN (R 3.6.0)
 glue          1.3.1   2019-03-12 [3] CRAN (R 3.5.3)
 htmltools     0.3.6   2017-04-28 [3] CRAN (R 3.5.0)
 knitr         1.23    2019-05-18 [3] CRAN (R 3.6.0)
 magrittr      1.5     2014-11-22 [3] CRAN (R 3.5.0)
 memoise       1.1.0   2017-04-21 [1] CRAN (R 3.6.0)
 packrat       0.5.0   2018-11-14 [1] CRAN (R 3.6.0)
 pkgbuild      1.0.3   2019-03-20 [3] CRAN (R 3.5.3)
 pkgload       1.0.2   2018-10-29 [3] CRAN (R 3.5.1)
 prettyunits   1.0.2   2015-07-13 [3] CRAN (R 3.5.0)
 processx      3.3.1   2019-05-08 [3] CRAN (R 3.6.0)
 ps            1.3.0   2018-12-21 [3] CRAN (R 3.5.2)
 R6            2.4.0   2019-02-14 [3] CRAN (R 3.5.2)
 Rcpp          1.0.1   2019-03-17 [3] CRAN (R 3.5.3)
 remotes       2.1.0   2019-06-24 [3] CRAN (R 3.6.0)
 rlang         0.4.0   2019-06-25 [1] CRAN (R 3.6.0)
 rmarkdown     1.13    2019-05-22 [1] CRAN (R 3.6.0)
 rprojroot     1.2     2017-01-16 [3] CRAN (R 3.5.0)
 rsconnect     0.8.13  2019-01-10 [1] CRAN (R 3.6.0)
 rstudioapi    0.10    2019-03-19 [3] CRAN (R 3.5.3)
 sessioninfo   1.1.1   2018-11-05 [3] CRAN (R 3.5.1)
 testthat      2.1.1   2019-04-23 [1] CRAN (R 3.6.0)
 usethis       1.5.0   2019-04-07 [3] CRAN (R 3.5.3)
 withr         2.1.2   2018-03-15 [3] CRAN (R 3.5.0)
 xfun          0.8     2019-06-25 [1] CRAN (R 3.6.0)
 yaml          2.2.0   2018-07-25 [3] CRAN (R 3.5.1)

[1] /home/joel/R/x86_64-pc-linux-gnu-library/3.6
[2] /usr/local/lib/R/site-library
[3] /usr/lib/R/site-library
[4] /usr/lib/R/library

[thomasp85]

I’m pretty sure you cannot control which device implementation is used by knitr — support for ragg is something you’ll have to take up with them

[joelgombin]

Ah? And yet the documentation of knitr (for the dev parameter) says:

if none of the 20 built-in devices is appropriate, we can still provide yet another name as long as it is a legal function name which can record plots (it must be of the form function(filename, width, height))

So I took it I could plug in any device in it? Am I wrong in thinking that?

[thomasp85]

I don't know about that functionality, honestly... but I can see a couple of issues. You are not passing in a function to dev but agg_png() which evaluates to NULL (probably why you get a pdf). Secondly agg_png() does not have the requested signature as it takes more than filename, width, and height...