Adding a letter to all table numbers in RMarkdown - r-markdown

Question

I'm using RMarkdown to create Supplementary documents for a paper. These supplements contain many tables. Let's call these documents Supplement A and Supplement B. I want the table numbering to reflect the supplement letter, that is, Table A1 or Table 1A for the first table in Supplement A and so on for all tables.
How can I modify the table numbering to add a letter into the table numbering schema?
Here's an example that will produce a table with normal numbering:
---
title: "Supplement A"
output: pdf_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
library(knitr)
library(kableExtra)
```
```{r cars}
kable(mtcars[1:5, ], booktabs=TRUE, caption="MTCars") %>%
kable_styling(latex_options="hold_position", position="left")
```

Answer 1

An inelegant solution using the captioner package (details provided here: https://datascienceplus.com/r-markdown-how-to-number-and-reference-tables/) can create captions and insert them manually just before the code chunk. Combining this with the Latex package caption makes it possible to remove the automatic table naming and numbering if the caption is generated within the code chunk (How to suppress automatic table name and number in an .Rmd file using xtable or knitr::kable?). I've done this in the YAML with \captionsetup[table]{labelformat=empty}, but it can be done in the document body also. Either way, the caption can then be generated within the code chunk, which was important in my case.
This solution stops bookdown referencing from working (because labelformat cannot be empty), but a workaround for table referencing was provided in the link for using the captioner package (and is included below).
---
title: "Supplement A"
header-includes:
- \usepackage{caption}
\captionsetup[table]{labelformat=empty}
output: pdf_document
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
library(knitr)
library(kableExtra)
library(captioner)
library(stringr)
```
```{r captions}
# Create the caption(s)
caption <- captioner("Table A", FALSE)
tab_1_cap <- caption("Tab_1", "MTCars")
# Create a function for referring to the tables in text
ref <- function(x) str_extract(x, "[^:]*")
```
The following table is `r ref(tab_1_cap)`.
```{r cars}
kable(mtcars[1:5, ], booktabs=TRUE, caption=tab_1_cap) %>%
kable_styling(latex_options="hold_position", position="left")
```

Answer 2

An alternative solution is avaiable via LaTeX. Add the following somewhere in the body of the document to change the default figure and table names to include the letter.
\def\figurename{Figure A}
\def\tablename{Table A}
To reference a table or figure in text use, e.g., Table A\#ref(tab:label), after defining the table label as normal.
This alone will leave a space in the table/figure caption (e.g., 'Table A 1' instead of 'Table A1'). This can be solved by adding the following to the YAML:
header-includes:
- \usepackage{caption}
- \DeclareCaptionLabelFormat{nospace}{#1#2}
- \captionsetup[figure]{labelformat=nospace}
- \captionsetup[table]{labelformat=nospace}
The \DeclareCaptionLabelFormat creates a function (here labeled nospace), which overrides the default caption label when called. #1 represents the label assigned to refer to tables or figures (e.g., 'Table A') and #2 represents the number of the table or figure. The captionsetup lines change the label format for all tables and figures to the format defined by 'nospace'.
Thus, the code produces, e.g., 'Table A1: Table name' as the caption. If instead you wanted, e.g., 'Table A-1: Table name', the code in \DeclareCaptionLabelFormat should be changed to {#1-#2}.
---
title: "Supplement A"
output: bookdown::pdf_document2
toc: false
header-includes:
- \usepackage{caption}
- \DeclareCaptionLabelFormat{nospace}{#1#2}
- \captionsetup[figure]{labelformat=nospace}
- \captionsetup[table]{labelformat=nospace}
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE)
library(knitr)
library(kableExtra)
library(bookdown)
```
\def\figurename{Figure A}
\def\tablename{Table A}
See Table A\#ref(tab:cars) for something about cars.
(ref:cars) Table caption
```{r cars}
kable(mtcars[1:5, ], booktabs=TRUE, caption="(ref:cars)") %>%
kable_styling(latex_options="hold_position", position="left")
```
Answer inspired by: Figure name in caption using RMarkdown
Caption latex package documentation: https://ctan.org/pkg/caption