25

Is it possible to display custom image (say png format) as geom_point in R ggplot? 

library(png)
pic1 <- readPNG("pic1.png")

png("Heatmap.png", units="px", width=3200, height=3200, res=300)
ggplot(data_frame, aes(medium, day, fill = Transactions))  +
   geom_tile(colour="white")  +
   facet_grid(dime3_year~dime3_month) + 
   scale_fill_gradient(high="blue",low="white") +
   theme_bw() + 
   geom_point(aes(dime3_channel, day, size=Conv,alpha=Conv,image=(annotation_raster(pic1,xmin=0,ymin=0,xmax=5,ymax=5)),color="firebrick")) +

Gives error:

Don't know how to automatically pick scale for object of type proto/environment. Defaulting to continuous Error: Aesthetics must either be length one, or the same length as the dataProblems:(annotation_raster(conv_pic, xmin = 0, ymin = 0, xmax = 5, ymax = 5))

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4
  • 1
    I would start with the grImport package. Some grid tinkering may be required. Commented Dec 24, 2014 at 16:26
  • 2
    See also grImport2, e.g. first example here, or Fig 11 with lattice here. Nice article on grImport here (see e.g. fig 8, also with lattice). Commented Dec 24, 2014 at 21:46
  • see also stackoverflow.com/questions/36133374/… Commented Mar 23, 2016 at 7:38
  • and stackoverflow.com/a/36172385/471093 Commented May 9, 2016 at 8:20

2 Answers 2

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15

The point geom is used to create scatterplots, and doesn't quite seem to be designed to do what you need, ie, display custom images. However, a similar question was answered here, which indicates that the problem can be solved in the following steps:

(1) Read the custom images you want to display,

(2) Render raster objects at the given location, size, and orientation using the rasterGrob() function,

(3) Use a plotting function such as qplot(),

(4) Use a geom such as annotation_custom() for use as static annotations specifying the crude adjustments for x and y limits as mentioned by user20650.

Using the code below, I could get two custom images img1.png and img2.png positioned at the given xmin, xmax, ymin, and ymax.

library(png)
library(ggplot2)
library(gridGraphics)
setwd("c:/MyFolder/")

img1 <- readPNG("img1.png")
img2 <- readPNG("img2.png")
g1 <- rasterGrob(img1, interpolate=FALSE)
g2 <- rasterGrob(img2, interpolate=FALSE)
qplot(1:10, 1:10, geom="blank") + 
  annotation_custom(g1, xmin=1, xmax=3, ymin=1, ymax=3) +
  annotation_custom(g2, xmin=7, xmax=9, ymin=7, ymax=9) +  
  geom_point()
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1 Comment

A picture of the result would have been great
7

DL Miller provided another solution using ggproto().https://github.com/dill/emoGG

library(ggplot2)
library(grid)
library(EBImage)
img <- readImage(system.file("img", "Rlogo.png", package = "png"))
RlogoGrob <- function(x, y, size, img) {
    rasterGrob(x = x, y = y, image = img, default.units = "native", height = size, 
        width = size)
}

GeomRlogo <- ggproto("GeomRlogo", Geom, draw_panel = function(data, panel_scales, 
    coord, img, na.rm = FALSE) {
    coords <- coord$transform(data, panel_scales)
    ggplot2:::ggname("geom_Rlogo", RlogoGrob(coords$x, coords$y, coords$size, 
        img))
}, non_missing_aes = c("Rlogo", "size"), required_aes = c("x", "y"), default_aes = aes(size = 0.05), 
    icon = function(.) {
    }, desc_params = list(), seealso = list(geom_point = GeomPoint$desc), 
    examples = function(.) {
    })

geom_Rlogo <- function(mapping = NULL, data = NULL, stat = "identity", 
    position = "identity", na.rm = FALSE, show.legend = NA, inherit.aes = TRUE, 
    ...) {
    layer(data = data, mapping = mapping, stat = stat, geom = GeomRlogo, 
        position = position, show.legend = show.legend, inherit.aes = inherit.aes, 
        params = list(na.rm = na.rm, img = img, ...))
}
ggplot(mtcars, aes(wt, mpg))+geom_Rlogo()
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