How to store r ggplot graph as html code snippet

Question

I am creating an html document by creating various objects with ggplotly() and htmltools functions like h3() and html(). Then I submit them as a list to htmltools::save_html() to create an html file.

I would like to add ggplot charts directly as images, rather than attaching all the plotly bells and whistles. In the end, I will create a self-contained html file (no dependencies), and the plotly stuff would make that file excessively large.

Is there some function that converts a ggplot object into some html-type object? Or do I have to save the ggplot as a .png file, then read the .png file into some object that I add to the list in the save_html() function?

My R code looks something like this:

library("tidyverse")
library("plotly")
library("htmltools")

HTMLOut <- "c:/Users/MrMagoo/My.html")
df <- data.frame(x=1:25, y=c(1:25*1:25))

g7 <- ggplot(df,aes(x=x, y=y)) + geom_point()
p7 <- ggplotly(g7)  # I would like to use something other than ggplotly here. Just capturing the ggplot as an image would be fine.

# create other objects to add to the html file
t7 <- h2(id="graph7", "Title for graph #7")
d7 <- p("description of graph 7")

save_html(list(t7, p7, d7), HTMLOut)
# of course, the real code has many more objects in that list – more graphs, text, tables, etc.

I would like to replace the plotly object (p7) with something that just presents g7 in a way that would not cause an error in the save_html function.

I had hoped to find a function that could directly Base64 encode a ggplot object, but it seems that I first need to output the 'ggplot' object as a .png file (or SVG, per Teng L, below), then base64-encode it. I was hoping there was a more direct way, but I may end up doing that, as in https://stackoverflow.com/a/33410766/3799203 , ending it with

g7img <- "<img src=\"data:image/png;base64,(base64encode string)\""
g7img <- htmltools::html(g7img)

Answer 1

If you want to save the plot as a dynamic plotly graph, you could use htmlwidgets::saveWidget. This will produce a stand-alone html file.

Here is a minimal example:

library(tidyverse);
library(plotly);
library(htmlwidgets);

df <- data.frame(x = 1:25, y = c(1:25 * 1:25))
gg <- ggplot(df,aes(x = x, y = y)) + geom_point()

# Save ggplotly as widget in file test.html
saveWidget(ggplotly(gg), file = "test.html");