Generate new slide from list of images

[baslat]

I am making a powerpoint presentation in quarto with R. I have a list of n images, and I have a list of n strings that describe the images. I would like each image to be on a new slide, accompanied by its description. How can I write code to dynamcially generate the slides?

It's similar to this (which I cannot get to work with quarto): https://stackoverflow.com/questions/11956520/r-knitr-markdown-output-plots-within-for-loop, and this (but not python): #954

Thanks!

Here's an example of what I'm working with (note I had to add a comment to the trailing backticks on theh code blocks to escape the formatting).

---
title: "Untitled"
format: pptx
---

```{r}
library(tidyverse)
cyls <- unique(mtcars$cyl)

make_plot <- function(cyls) {
mtcars  |>
        filter(cyl == cyls) |>
        ggplot(aes(x = mpg, y = hp)) +
        geom_point() +
        labs(title = paste(cyls,"cylinders"))
}

plots <- purrr::map(cyls, make_plot)

descs <- list(
    "These cars are good",
    "These cars are fun",
    "I have no opinion on these cars")
```#neededasescape



<!-- Done manually -->

## 6 Cyls

`r descs[[1]]`

```{r}
print(plots[[1]])
```#neededasescape

## 4 Cyls

`r descs[[2]]`

```{r}
print(plots[[2]])
```#neededasescape


## 8 Cyls

`r descs[[3]]`

```{r}
print(plots[[3]])
```#neededasescape

[cderv]

I believe this answer regarding gt tables created dynamically can help understand how you could do that with knitr. This is linking to resources already working in R Markdown ecosystem.

#2370 (comment)

Without your example, I would do that

---
title: "Untitled"
format: pptx
---

```{r, include=FALSE}
library(tidyverse)
cyls <- unique(mtcars$cyl)

descs <- c(
    "These cars are good",
    "These cars are fun",
    "I have no opinion on these cars")

```

```{r}
#| output: asis
src <- purrr::map2_chr(cyls, descs, \(cyls, desc) {
  knitr::knit_expand(text = c(
    "## {{ cyls }} Cyls",
    "",
    "{{ desc }}",
    "",
    "",
    "```{r}",
    "#| echo: true",
    "mtcars  |>",
    "  filter(cyl == {{ cyls }}) |>",
    "  ggplot(aes(x = mpg, y = hp)) +",
    "  geom_point() +",
    "  labs(title = paste(cyls,'cylinders'))",
    "```",
    ""))
})
res <- knitr::knit_child(text = src, quiet = TRUE)
cat(res, sep = '\n')
```

This will create 4 slides with the content you want to iterate on

This can be tweak by using knit_child only and using an external child document, or template to user.

Hope it helps understand what knitr offers for this kind of usage.

[baslat]

Beautiful, thank yoo so much!

[baslat]

Do you know how I could modify this to use an existing list of ggplots, instead of the code to create the plots?

[baslat]

My hacky solution for the existing list is as follows (assuming plots is a list of 3 charts):

```{r}
plots <- list(chart1, chart2, chart3)
index <- 1:3
```


```{r make_charts}
#| output: asis
src <- purrr::map_chr(index, \(index) {
  knitr::knit_expand(text = c(
    "## Some title",
    "",
    "Words here, could be from a desc",
    "",
    "",
    "```{r}",
    "#| echo: false",
    "plots[[{{ index }}]]",
    "```",
    ""))
    }
    )
res <- knitr::knit_child(text = src, quiet = TRUE)
cat(res, sep = '\n')

```

[cderv]

Yes this works. For a list of object, I would not use knit_expand(), just knit_child().

---
title: "Untitled"
format: pptx
keep-md: true
---

```{r}
library(tidyverse)
cyls <- unique(mtcars$cyl)

make_plot <- function(cyls) {
  mtcars  |>
    filter(cyl == cyls) |>
    ggplot(aes(x = mpg, y = hp)) +
    geom_point() +
    labs(title = paste(cyls,"cylinders"))
}

plots <- purrr::map(cyls, make_plot)

descs <- list(
    "These cars are good",
    "These cars are fun",
    "I have no opinion on these cars")

tabs <- tibble::tibble(
  cyls = cyls,
  plots = plots,
  descs = unlist(descs)
)
```


```{r}
#| output: asis
res <- purrr::pmap_chr(tabs, \(cyls, plots, descs) {
  knitr::knit_child(text = c(
    "## `r cyls` Cyls",
    "",
    "`r descs`",
    "",
    "",
    "```{r}",
    "#| echo: false",
    "plots",
    "```",
    ""), envir = environment(), quiet = TRUE)
})
cat(res, sep = '\n')
```

I let you try to understand this example, and tweak it to your need.