Using !expr in 'label:' chunk option is not possible?

[r-scotti]

Hello.
In the small test below the last chunk doesn't compile.
If I substitute the first line: <#| label: !expr taste0("tbl-", tab)>
with <#| label: tbl-tables>, the output is as expected.
Is it just not possible to use "!expr" in the 'Label:' chunk option?
Many thanks, Roberto

Details
quarto::quarto_version() ‘0.9.238’ (how to upgrade?)
System: Ubuntu 20.04

Sys.info()
sysname: "Linux"
release: "5.15.0-76-generic"
version: "#83~20.04.1-Ubuntu SMP Wed Jun 21 20:23:31 UTC 2023"
Below: Example Quarto code

---
format: pdf
---

```{r}
library(tidyverse)
library(kableExtra)
x <- c(3, 1, 2)
Table1 <- data.frame(A = x, B = letters[x])
x <- c(11, 16, 21)
Table2 <- data.frame(C = x, D = letters[x])

tab <- "Table1"
```

OK with "#| label: tbl-tables"

```{r}
#| label: !expr paste0("tbl-", tab)
#| tbl-cap: !expr paste("This is", tab)
#| tbl-subcap:
#|   - "first"
#|   - "second"

tbl <- get(tab)

kbl(tbl)

tibble(attribute = names(tbl)) |> 
  unnest(cols = c(attribute)) |> 
  mutate(kind = typeof(attribute)) |> 
  kbl()
```

[mcanouil]

Could you format properly your post? In its current shape it is not quite legible.
For instance don't use title for text.

See https://quarto.org for your question about upgrade.

---

You can share a Quarto document using the following syntax, i.e., using more backticks than you have in your document (usually four ````).

````qmd
---
title: "Reproducible Quarto Document"
format: html
---

This is a reproducible Quarto document using `format: html`.
It is written in Markdown and contains embedded R code.
When you run the code, it will produce a plot.

```{r}
plot(cars)
```

The end.
````

[r-scotti]

I apologise, hope it is ok now

[cscheid]

This isn't a quarto problem, it's a knitr one:

$ R
> knitr:::knit("6210.qmd")


processing file: 6210.qmd
  |..................                                                    |  25%
  ordinary text without R code

  |...................................                                   |  50%
label: unnamed-chunk-1
  |....................................................                  |  75%
  ordinary text without R code

  |......................................................................| 100%
Quitting from lines 19-33 (6210.qmd)
Error in defaults[[name]] : invalid subscript type 'list'

[mcanouil]

@r-scotti you should report this in knitr repository, see https://github.com/yihui/knitr.

[r-scotti]

Many thanks! Your redirection towards knitr has been the key to solve my problem.
I immediately referred to GitHub Kintr site where I found that an analogous question had already been answered.
I developed my solution based on https://stackoverflow.com/questions/12095113/r-knitr-possible-to-programmatically-modify-chunk-labels
Excuse me again for the errors.
Roberto

[cderv]

FWIW knitr does not support using a R object / expression as a label.

This is because the labels are determined before any code chunk is evaluated (i.e., they are determined at the parsing stage): yihui/knitr@0e9bb8b/R/parser.R#L197-L198 When parsing the document, the parser doesn't know the value of any objects.

Related discussion: rstudio/bookdown#1419 (comment)

[r-scotti]

Many thanks! I could imagine but I do not know how I could find the answer you are giving me. While compiling the question in knitr GitHub site, a question tightly related to mine came up and I discovered that using knitr::knit_extend() it is possible (though not straightforward at all!) to obtain my goal: "produce many cross-referenceable nicely formatted (with label, cap and sub-caps) table pairs, writing the code only once." Roberto Il giorno lun 17 lug 2023 alle ore 15:40 Christophe Dervieux < ***@***.***> ha scritto:

…

FWIW *knitr* does not support using a R object / expression as a label. This is because the labels are determined before any code chunk is evaluated (i.e., they are determined at the parsing stage): ***@***.***/R/parser.R#L197-L198 <https://github.com/yihui/knitr/blob/0e9bb8bc8cd77b2b8ace872637bb86a5b6d54bcb/R/parser.R#L197-L198> When parsing the document, the parser doesn't know the value of any objects. Related discussion: rstudio/bookdown#1419 (comment) <rstudio/bookdown#1419 (comment)> — Reply to this email directly, view it on GitHub <#6210 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEAKXD2YUX6XJ4TUZOOSV3DXQU6FTANCNFSM6AAAAAA2KFFVTA> . You are receiving this because you were mentioned.Message ID: ***@***.***>

-- Roberto Scotti <https://scholar.google.it/citations?hl=en&user=EgZYcIAAAAAJ&view_op=list_works&sortby=pubdate> - Nuoro Forestry School <https://www.facebook.com/NuoroForestrySchoolUniSS/> Dip. Agraria <https://www.uniss.it/ugov/person/2496> - ***@***.*** ORCID iD <https://orcid.org/0000-0001-7394-4473> Publons <https://publons.com/researcher/1104101/roberto-scotti/> IRIS <https://iris.uniss.it/cris/rp/rp02644>

--

-- *Dona il  5x1000* all'Università degli Studi di Sassaricodice fiscale: 00196350904

[cderv]

I could imagine but I do not know how I could find the answer you are
giving me.

It is not straightforward as knitr does not really allow passing computed variable to label.

We document stuff like knit_expand() and child document in the R Markdown cookbook (which has knitr recipes which apply to quarto)

• https://bookdown.org/yihui/rmarkdown-cookbook/knit-expand.html
• https://bookdown.org/yihui/rmarkdown-cookbook/child-document.html