dml: Wrap plot instructions for DrawingML plotting in Powerpoint

Description

A simple wrapper to mark the plot instructions as Vector Graphics instructions. It produces an object of class 'dml' with a corresponding method ph_with.

The function enables usage of any R plot with argument code and with ggplot objects with argument ggobj.

Note: the output is a vector graphic, not a native Microsoft Office chart. The underlying data is not embedded in the document.

Usage

dml(
  code,
  ggobj = NULL,
  bg = "white",
  fonts = list(),
  pointsize = 12,
  editable = TRUE,
  ...
)

Arguments

code: plotting instructions
ggobj: ggplot object to print. argument code will be ignored if this argument is supplied.
bg, fonts, pointsize, editable: Parameters stored and later passed to dml_pptx by ph_with.dml.
...: unused arguments

background color

When dealing with a ggplot object, the bg parameter sets the device background but the ggplot theme's plot.background will typically draw over it. To control the background appearance, set it in the theme instead:

theme(
  panel.background = element_rect(fill = "#EFEFEF"),
  plot.background = element_rect(fill = "wheat"))

Limitations

The DrawingML format does not support the following R graphics features:

Patterns and gradients: grid patterns (GridPattern), linear and radial gradients used as fill are not translated into DrawingML. ggplot2 will emit a warning when these are used.
Rich text (ggtext/gridtext): packages such as ggtext render HTML/Markdown into composite grid grobs. The rvg device can only capture low-level primitives (text strings, lines, polygons), so the rich formatting (inline images, coloured spans, HTML markup) is lost. Use standard ggplot2 text functions or apply formatting after export in PowerPoint.
Plotmath expressions: R's graphics engine decomposes expression() into individual text primitives before the device sees them. Compound expressions (e.g. expression("a" * "b"), superscripts, subscripts) are rendered as separate text boxes, causing vertical misalignment.
Clipping paths, masks, compositing and transformations: these R >= 4.1 features have no DrawingML equivalent and are silently ignored.

Examples

Run this code

anyplot <- dml(code = barplot(1:5, col = 2:6), bg = "wheat")

library(officer)
doc <- read_pptx()
doc <- add_slide(doc, "Title and Content", "Office Theme")
doc <- ph_with(doc, anyplot, location = ph_location_fullsize())
fileout <- tempfile(fileext = ".pptx")
# fileout <- "vg.pptx"
print(doc, target = fileout)