Plotting many circles with different radii

[Sara Williams]

Hello group,

I'm interested in plotting many circles (45k) all with centers at (0,0) and each with a different radius. This seems basic enough but I've had a real bear of a time getting a plot to work and I cannot find a help post that would allow me to be able to do this. However, my reading leads me to think that geom_point with scale_radius or scale_size is my best bet. Still, I have been unable to produce a plot that has accurate circle sizes according to my radius scale.

Basically, I am plotting animal movement step length (across all possible angles of the circle) and have used models and simulation to obtain 45k steps - these will equal the radii of my circles. Using a transparency value, I'd like to indicate the step lengths that have a higher probability of being simulated (there will be many more circles with smaller radii and resultantly the plot will be darker in the center and lighter toward the edges).

Example data:

z <- seq(0, 10000, length.out = 45000) # radii (step lengths)

x <- rep(0, length(z)) # x center for each circle

y <- rep(0, length(z)) # y center for each circle

points <- data.frame(x, y, z)

points <- dplyr::arrange(points, by = z)

p  <- ggplot(points) + 

        geom_point(aes(x, y, size = z), colour = "darkred", alpha = 0.05) +

        scale_radius(range = c(0, 10000), guide = FALSE)

Any thoughts or insight on how to ensure that the radii of the points are in fact aligned with the radii I have in my data frame would be greatly appreciated. Or any different approaches to plotting concentric circles with varying radii would be quite helpful as well.

Thanks a lot,

Sara 

[Hadley Wickham]

I think the key is to use scale_size_identity().

And you'll probably need to read
https://cran.r-project.org/web/packages/ggplot2/vignettes/ggplot2-specs.html
to get the details exactly right.

Hadley

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