I’m using rmarkdown to produce a number of reports for my employer (example: https://filer.skane.se/kommunrapporter/Kommunrapport_Kristianstad.html ). From September we need to improve the accessibility for visual impaired of all our web documents (following an EU regulation). There are many things that need to be changed, but I have identified two major issues. 1) It must be possible to move between headings and links with TAB.2) Figures need to be provided with an “ alt - text ”-attribute. Does anyone have a solution or is able to point me to the right direction?
If anybody want to help me, I provide a simple test case below:
---
title: "Accessibility"
author: "C Lindell"
date: '2020-06-23'
output:
html_document:
toc: yes
toc_float: yes
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE, warning = FALSE, message = FALSE)
```
# Navigate with the TAB-key?
I want to navigate the toc with the TAB-key and go to the right part of the document by pressing RETURN. I also want to be able to tab between links and headings.
# Diagrams and pictures
How do I provide a generated diagram with a "alt text"-tag to make it readable for the vison impaired?
```{r}
library(ggplot2)
ggplot(cars, aes(speed, dist)) +
geom_line()
```
When you enclose your Rmd file with four backticks instead of the standard three we will be able to see the unformatted Rmd file.
No answers yet: no R installation on my phone.
Big thanks to HanOostdijk and radovan! Your solutions have really helped me, but I seems a bit to complicated to add an "alt-text"-label. Soon we have to adapt all documents from public organizations in the EU to make them readable to people with visual impairments. It would help if rmarkdown could distinguish between "caption" and "alt-text". The text in "alt-text" must explain the contents of the chart or image, while "caption" contains only the title. This could be a win or loose feature for rmarkdown in the public sector. I hope someone could add that feature to rmarkdown (I don't have the technical skills myself). And the html-documents produced by rmarkdown must be possible to navigate with the keyboard.
@ChristianL,
you already referred to https://forum.posit.co/t/adding-alt-text-to-figures-generated-in-r-markdown/65191. I am afraid that that is the way to go until the knitr package is changed: you would have to change the knit hook for the plot.
While that is not so difficult to do (the reference shows how in the case of a Hugo document) the problem lies more in handling correctly all the different cases.
Therefore I suggest you do a request in the knitr GitHub repository .
having the caption showed on the surface, without alt text under the hood.
It seems that there is no perfect solution (with knitr), as pointed by @HanOostdijk.
this is an example of a knitr plot hook that supports only the arguments caption and alt.
All other arguments you would like to use you should include yourself.
For my convenience I also used nocaption and noalt but because these are not recognized they have the same meaning as not specifying caption resp. alt .
---
author: "C Lindell"
title: "my title"
date: '2020-06-24'
output:
html_document:
toc: yes
toc_float: yes
keep_md: yes
---
```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = FALSE, warning = FALSE, message = FALSE)
knitr::knit_hooks$set(plot = function(x,options) {
base = knitr::opts_knit$get('base.url')
if (is.null(base)) base = ''
alt = ifelse (is.null(options$alt),"",options$alt)
cap = ifelse (is.null(options$caption),"",options$caption)
if (alt != ""){
sprintf('', cap, base, x, alt)
} else {
sprintf('', cap, base, x)
}
})
```
# Diagrams and pictures
How do I provide a generated diagram with a "alt text"-tag to make it readable for the vision impaired?
```{r}
library(ggplot2)
```
### plot with caption and alt_text
```{r plot1,caption='nice plot',alt='my alt_text'}
ggplot(cars, aes(speed, dist)) +
geom_line()
```
### plot without caption and with alt_text
```{r plot2,nocaption='nice plot',alt='my alt_text'}
ggplot(cars, aes(speed, dist)) +
geom_line()
```
### plot with caption and without alt_text
```{r plot3,caption='nice plot',noalt='my alt_text'}
ggplot(cars, aes(speed, dist)) +
geom_line()
```
The last issue you mentioned was probably a bug of Pandoc. If you use knitr::include_graphics() to include the image, the alt attribute shouldn't be empty.