ggpath: Robust Image Rendering Support for 'ggplot2'

Description

A 'ggplot2' extension that enables robust image grobs in panels and theme elements.

Usage

GeomFromPath

GeomRefLines

Format

An object of class GeomFromPath (inherits from Geom, ggproto, gg) of length 5.

An object of class GeomRefLines (inherits from Geom, ggproto, gg) of length 5.

Author(s)

Maintainer: Sebastian Carl mrcaseb@gmail.com [copyright holder]

See Also

Useful links:

• https://github.com/mrcaseb/ggpath

• https://mrcaseb.github.io/ggpath/

• Report bugs at https://github.com/mrcaseb/ggpath/issues

Theme Elements for Image Grobs

Description

In conjunction with the ggplot2::theme() system, the element_ functions specify the display of how non-data components of a ggplot are drawn. Both functions call magick::image_read() to process image files from valid image URLs, local paths, raster objects, or bitmap arrays.

• element_path(): draws images as replacement for ggplot2::element_text(). Use this to replace text with images.

• element_raster(): draws images as replacement for ggplot2::element_rect(). Use this to put images in plot background.

Usage

element_path(
  alpha = NULL,
  colour = NA,
  hjust = NULL,
  vjust = NULL,
  color = NULL,
  angle = NULL,
  size = 0.5
)

element_raster(
  image_path,
  x = grid::unit(0.5, "npc"),
  y = grid::unit(0.5, "npc"),
  width = grid::unit(1, "npc"),
  height = grid::unit(1, "npc"),
  just = "centre",
  hjust = NULL,
  vjust = NULL,
  interpolate = TRUE,
  default.units = "npc",
  name = NULL,
  gp = NULL,
  vp = NULL
)

Arguments

Details

To be able to use the functions correctly, a basic understanding of how they work is required.

element_path() can be applied wherever ggplot2::element_text() is usually used. It replaces text with an image if the text is a valid image file location or data.

element_raster() can be applied wherever ggplot2::element_rect() is usually used. A path in the sense of magick::image_read() must be explicitly specified here because it cannot read plot data. It is designed exclusively for inserting an image into the background of a plot and calls grid::rasterGrob() internally. Neither width nor height need to be specified, in which case, the aspect ratio of the image is preserved. If both width and height are specified, it is likely that the image will be distorted.

Value

An S3 object of class element.

See Also

geom_from_path(), grid::rasterGrob(), grid::unit(), magick::image_read()

Examples

library(ggplot2)
library(ggpath)

# compute paths of R logo file and background image file shipped with ggpath
local_r_logo <- system.file("r_logo.png", package = "ggpath")
local_background_image <- system.file("example_bg.jpg", package = "ggpath")

# create dataframe with x-y-coordinates and the above local path
plot_data <- data.frame(x = c(-1, 1), y = 1, path = local_r_logo)

# Replace title, subtitle, the caption, axis labels as well as y-axis text
# the the local image
ggplot(plot_data, aes(x = x, y = local_r_logo)) +
  theme_minimal() +
  labs(
    title = local_r_logo,
    subtitle = local_r_logo,
    x = local_r_logo,
    y = local_r_logo,
    caption = local_r_logo
  ) +
  theme(
    plot.caption = element_path(hjust = 1, size = 0.6),
    axis.text.y = element_path(size = 1),
    axis.title.x = element_path(),
    axis.title.y = element_path(vjust = 0.9),
    plot.title = element_path(hjust = 0, size = 2, alpha = 0.5),
    plot.subtitle = element_path(hjust = 0.9, angle = 45),
  )

# Use local image as plot background
ggplot(plot_data, aes(x = x, y = y)) +
  geom_from_path(aes(path = path), width = 0.2) +
  coord_cartesian(xlim = c(-2, 2)) +
  theme_dark() +
  theme(
    plot.background = element_raster(local_background_image),
    panel.background = element_rect(fill = "transparent")
  )

ggplot2 Layer for Visualizing Images from URLs or Local Paths

Description

This geom is used to plot images instead of points in a ggplot. It requires x, y aesthetics as well as a path.

Usage

geom_from_path(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = TRUE
)

Arguments

Value

A ggplot2 layer (ggplot2::layer()) that can be added to a plot created with ggplot2::ggplot().

Aesthetics

geom_from_path() understands the following aesthetics (required aesthetics have no default value):

x

The x-coordinate. Required.

y

The y-coordinate. Required.

path

a file path, url, raster object or bitmap array. See magick::image_read() for further information. Required.

alpha = NULL

The alpha channel, i.e. transparency level, as a numerical value between 0 and 1.

colour = NULL

The image will be colorized with this colour. Use the special character "b/w" to set it to black and white. For more information on valid colour names in ggplot2 see https://ggplot2.tidyverse.org/articles/ggplot2-specs.html?q=colour#colour-and-fill

angle = 0

The angle of the image as a numerical value between 0° and 360°.

hjust = 0.5

The horizontal adjustment relative to the given x coordinate. Must be a numerical value between 0 and 1.

vjust = 0.5

The vertical adjustment relative to the given y coordinate. Must be a numerical value between 0 and 1.

width = 1.0

The desired width of the image in npc (Normalised Parent Coordinates). The default value is set to 1.0 which is big but it is necessary because all used values are computed relative to the default. A typical size is width = 0.1 (see below examples).

height = 1.0

The desired height of the image in npc (Normalised Parent Coordinates). The default value is set to 1.0 which is big but it is necessary because all used values are computed relative to the default. A typical size is height = 0.1 (see below examples).

Examples

library(ggplot2)
library(ggpath)

# compute path of an R logo file shipped with ggpath
local_image_path <- system.file("r_logo.png", package = "ggpath")

# create dataframe with x-y-coordinates and the above local path
plot_data <- data.frame(x = c(-1, 1), y = 1, path = local_image_path)

# plot images directly from local path
ggplot(plot_data, aes(x = x, y = y)) +
  geom_from_path(aes(path = path), width = 0.2) +
  coord_cartesian(xlim = c(-2, 2)) +
  theme_minimal()

# plot images directly from local path and apply transparency
ggplot(plot_data, aes(x = x, y = y)) +
  geom_from_path(aes(path = path), width = 0.2, alpha = 0.5) +
  coord_cartesian(xlim = c(-2, 2)) +
  theme_minimal()

# It is also possible and recommended to use the underlying Geom inside a
# ggplot2 annotation
ggplot() +
  annotate(
    ggpath::GeomFromPath,
    x = 0,
    y = 0,
    path = local_image_path,
    width = 0.4
  ) +
  theme_minimal()

ggplot2 Layer for Horizontal and Vertical Reference Lines

Description

These geoms can be used to draw horizontal or vertical reference lines in a ggplot. They use the data in the aesthetics x0 and y0 to compute their median or mean and draw them as a line.

Usage

geom_median_lines(
  mapping = NULL,
  data = NULL,
  ...,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

geom_mean_lines(
  mapping = NULL,
  data = NULL,
  ...,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Arguments

Value

A ggplot2 layer (ggplot2::layer()) that can be added to a plot created with ggplot2::ggplot().

Aesthetics

geom_median_lines() and geom_mean_lines() understand the following aesthetics (at least one of the x0 or y0 aesthetics is required):

x0

The variable for which to compute the median/mean that is drawn as vertical line.

y0

The variable for which to compute the median/mean that is drawn as horizontal line.

alpha = NA

The alpha channel, i.e. transparency level, as a numerical value between 0 and 1.

color = "red"

The color of the drawn lines.

linetype = 2

The linetype of the drawn lines.

size = 0.5

The size of the drawn lines. Deprecated as of ggplot2 v3.4.0, use linewidth instead.

linewidth = 0.5

The width of the drawn lines. Starting at ggplot2 v3.4.0.

See Also

The underlying ggplot2 geoms ggplot2::geom_hline() and ggplot2::geom_vline()

Examples

library(ggplot2)

# inherit top level aesthetics
ggplot(mtcars, aes(x = disp, y = mpg, y0 = mpg, x0 = disp)) +
  geom_point() +
  geom_median_lines() +
  geom_mean_lines(color = "blue") +
  theme_minimal()

# draw horizontal line only
ggplot(mtcars, aes(x = disp, y = mpg, y0 = mpg)) +
  geom_point() +
  geom_median_lines() +
  geom_mean_lines(color = "blue") +
  theme_minimal()

# draw vertical line only
ggplot(mtcars, aes(x = disp, y = mpg, x0 = disp)) +
  geom_point() +
  geom_median_lines() +
  geom_mean_lines(color = "blue") +
  theme_minimal()

# choose your own value
ggplot(mtcars, aes(x = disp, y = mpg)) +
  geom_point() +
  geom_median_lines(x0 = 400, y0 = 15) +
  geom_mean_lines(x0 = 150, y0 = 30, color = "blue") +
  theme_minimal()