How to store r ggplot graph as html code snippet

问题

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)

回答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");

回答2:

I ended up generating a temparory image file, then base64 encoding it, within a function I called encodeGraphic() (borrowing code from LukeA's post):

library(ggplot2)
library(RCurl)
library(htmltools)
encodeGraphic <- function(g) {
  png(tf1 <- tempfile(fileext = ".png"))  # Get an unused filename in the session's temporary directory, and open that file for .png structured output.
  print(g)  # Output a graphic to the file
  dev.off()  # Close the file.
  txt <- RCurl::base64Encode(readBin(tf1, "raw", file.info(tf1)[1, "size"]), "txt")  # Convert the graphic image to a base 64 encoded string.
  myImage <- htmltools::HTML(sprintf('<img src="data:image/png;base64,%s">', txt))  # Save the image as a markdown-friendly html object.
  return(myImage)
}

HTMLOut <- "~/TEST.html"   # Say where to save the html file.
g <- ggplot(mtcars, aes(x=gear,y=mpg,group=factor(am),color=factor(am))) + geom_line()  # Create some ggplot graph object
hg <- encodeGraphic(g)  # run the function that base64 encodes the graph
forHTML <- list(h1("My header"), p("Lead-in text about the graph"), hg)
save_html(forHTML, HTMLOut)  # output it to the html file.

回答3:

I think what you want may be close to one of the following:

Seems you are creating an HTML report but hasn't checked out RMarkdown. It comes with Base64 encode. When you create an RMarkdown report, pandoc automatically converts any plots into an HTML element within the document, so the report is self-contained.
SVG plots. This is less likely to be what you might want, but SVG plots are markup-language based and may be easily portable. Specify .svg extension when you use ggsave() and you should be getting an SVG image. Note that SVG is an as-is implementation of the plot, so if can be huge in file size if you have thousands of shapes and lines.

来源：https://stackoverflow.com/questions/50244709/how-to-store-r-ggplot-graph-as-html-code-snippet

标签

ggplot2

htmltools