Further integration with knitr?

[yihui]

Finally I have a chance to play with this package and think about better integration with knitr: https://twitter.com/thomasp85/status/1021462758007672834 :)

I don't know what chunk options you need from knitr (it appears that gganimate already works amazingly well in R Markdown), but currently I wonder if the three chunk options fig.width, fig.height, and dev can be supported (you may also need to use dpi).

```{r, fig.width=4, fig.height=10}
library(ggplot2)
library(gganimate)

ggplot(mtcars, aes(factor(cyl), mpg)) + 
  geom_boxplot() + 
  # Here comes the gganimate code
  transition_states(
    gear,
    transition_length = 2,
    state_length = 1
  ) +
  enter_fade() + 
  exit_shrink() +
  ease_aes('sine-in-out')
```

[thomasp85]

Some of the thoughts I’ve had regarding this is to be able to specify some of the arguments to animate as chink options so that you could define which renderer to use, the number of frames, framerate etc

This would allow you to not have to end with a call to animate() in order to costumize the animation settings

[thomasp85]

A big departure from the current animation support is that the number of frames in the animation is free to choose

[yihui]

For the knit_print.gganim method:

gganimate/R/gganim.R

Lines 23 to 26 in ef2e717

	knit_print.gganim <- function(x, ...) {
	anim <- animate(x)
	knitr::knit_print(anim)
	}

You are actually free to use any chunk options, e.g.,

knit_print.gganim <- function(x, options, ...) {
  anim <- do.call(animate, c(list(x, device = options$dev), options$gganimate.options)
  knitr::knit_print(anim)
}

Here the chunk option gganimate.options is just an example (you could use a different option name).

Then users can pass any arguments to animate, e.g.,

```{r, gganimate.options = list(renderer = ffmpeg_renderer())}
```

Supporting fig.width and fig.height can be a little bit tricky because I use inch as the unit for all graphical devices, e.g.,
https://github.com/yihui/knitr/blob/01407a72c8d3497336487029b21189ad13bee498/R/plot.R#L81 (if you want, I can export this function).

[thomasp85]

Ah - didn't know you could just create your own options. In that case I don't think there is anything more that knitr should do...

I think I'll just make my own device dimension solution as I don't currently support all devices in gganimate

What is your stance on namespacing options? Would you prefer to have one gganimate.options or is it ok to have all options as separate ones?

[thomasp85]

BTW, slightly tangential to this issue - have you had any experience with animations in pdf using the tikz and animate latex packages?

How would one potentially support this in knit_print

[yihui]

Good question on namespacing options. That has actually been a minor headache of mine, because knitr doesn't have any constraints on what options you can provide or use. So far I haven't seen bad consequences (like two package authors happen to use the same option for different purposes). I slightly prefer a single option gganimate.options = list() (if the name gganimate.options feels too long, gganimate also sounds okay to me).

Re: animations in PDF, yes, when fig.show='animate' and the output format is LaTeX, the LaTeX package animate will be used (the animation can only be viewed in Acrobat Reader). In your case, when knitr::is_latex_output(), I think you can just draw all plots. There is nothing else you need to do, since knitr should be able to handle the animation automatically. For R Markdown documents, \usepackage{animate} in the preamble will be needed (I should have automated this).

[thomasp85]

@yihui I'm toying with pdf output, and knitr_print.gganim() now just writes a bunch of pdf files - it does seem like knitr is still using ffmpeg for conversion and not a native latex solution, and the resulting pdf does not contain any animation...

If you have the time could you see if it is something in my setup that is not working - an example RMarkdown doc is below. You'll need the latest gganimate from GitHub

---
title: "PDF Animation Test"
output: pdf_document
header-includes:
   - \usepackage{animate}
---

`gganimate` now supports animations inside PDF documents. This feature is only 
viewable with Acrobat Reader, however. Remember to include 
`\usepackage{animate}` in the preamble and set `fig.show='animate'` in the chunk
options:

```{r, fig.show='animate'}
library(gganimate)
ggplot(airquality, aes(Day, Temp, group = Month)) + 
  geom_line() + 
  transition_reveal(Month, Day)
```

[yihui]

Fixed in the dev version of knitr!

[thomasp85]

Yay - will test once I get a computer again

[Frank-Sw]

---

title: "PDF Animation Test"
output: pdf_document
header-includes:

• \usepackage{animate}

---

gganimate now supports animations inside PDF documents. This feature is only
viewable with Acrobat Reader, however. Remember to include
\usepackage{animate} in the preamble and set fig.show='animate' in the chunk
options:

library(gganimate)
ggplot(airquality, aes(Day, Temp, group = Month)) + 
  geom_line() + 
  transition_reveal(Month, Day)

Does not work for me;

Always turn "PDF_Animation_Test_files/figure-latex/animation-%d.pdf: No such file or directory"

Could anyone of you guide me? Thanks.

[thomasp85]

have you installed the GitHub version of knitr?