[R] plotting circles with symbols()

[Peter Ehlers]

The circle is not "too large"; it just uses your x-units for the
radius and your plotting region isn't square.
Here are some things to try:

plot(0, 0, xlim = c(-1, 1), ylim = c(-1, 1))
symbols(0, 0, circles = 1, inches = FALSE, add = TRUE)
abline(v = c(-1,1)) # shows that x-units 'fit'
abline(h = c(-1,1)) # shows that y-units don't fit

par(pty = "s") # set up square plot
plot(0, 0, xlim = c(-1, 1), ylim = c(-1, 1))
symbols(0, 0, circles = 1, inches = FALSE, add = TRUE)

# set the y/x-aspect (see ?plot.window)
plot(0, 0, xlim = c(-1, 1), ylim = c(-1, 1), asp = 1)
symbols(0, 0, circles = 1, inches = FALSE, add = TRUE)

  -Peter Ehlers

eariasca wrote:
> Hello,
> 
> I am not able to plot a circle of a given radius using symbols().  In 
> the example below, the circle appears too large:
> 
> plot(0, 0, xlim = c(-1, 1), ylim = c(-1, 1))
> symbols(0, 0, circles = 1, inches = FALSE, add = TRUE)
> 
> What's happening?
> 
> Ery
> 
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> 

-- 
Peter Ehlers
University of Calgary
403.202.3921