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How to add an image as data points on a map in R

I am using a map map in R to draw a simple geographic map and then put my data into it.

My question is if there is any way in R to represent data points with a picture of interest, such as an animal that I am working on in my example.

This is just to better represent the distribution of my data points relative to each other for my reader.

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3 answers


You can also use a mesh package. grid.raster

can be used to place some images.

Since it maps

is a graphics base package, you need to gridBase

merge the grid / base graphics.

Here's an example:



library(maps)
map('usa',boundary=T,fill=T,col='grey')
library(gridBase)
library(grid)
library(png)
vps <- baseViewports()
pushViewport(vps$figure,vps$plot)
camel <- readPNG("camel.png")    ## some animal picture
grid.rect(gp = gpar(fill=NA))

x <- c(-110,-100,-70)
y <- c(30,40,40)

grid.raster(image=camel,x=x,y=y,width=5,   ## it is vectorized
            interpolate=FALSE,default.units = 'native')
upViewport(1)

enter image description here

PS: I'm not sure there are camels in the USA ...

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rasterImage

is one way, albeit somewhat laborious. Once you have images of interest as bitmap objects, you can place them at specific locations (and frame sizes) within your plot area.



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In addition to the feature rasterImage

mentioned by @CarlWitthoft, there is also a combination my.symbols

and ms.image

from the TeachingDemos package for adding images to a plot (basic graphics). The approach rasterImage

gives the most control, but is my.symbols

more like a normal plotting function in which you say draw images centered in those coordinates (and set other parameters to specify size, etc.).

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