Drawing Circles in R

drawing circle in R

You need to specify asp = 1:

x = runif(100, -1, 1)
y = runif(100, -1, 1)
plot(x, y, asp = 1, xlim = c(-1, 1))
draw.circle(0, 0, 1, nv = 1000, border = NULL, col = NA, lty = 1, lwd = 1)

EDIT: Just a side note, you can make your Monte Carlo function more efficient:

mc.pi = function(n) {

  x = runif(n, -1, 1)
  y = runif(n, -1, 1)
  pin = sum(ifelse(sqrt(x^2 + y^2 <= 1), 1, 0))
  4 * pin/n
}

Drawing a series of circles in R

This is basically @Peter's answer but with modifications. Your approach was fine but there is no radius= argument in DrawCircle. See the manual page ?DrawCircle for the arguments:

dev.new(width=12, height=4)
Canvas(xlim = c(0,50), ylim=c(2, 6), asp=1, xpd=TRUE)
DrawCircle(x=plotdat$xcords, y=plotdat$ycords, r.out = 2)

But your example has axes:

plot(NA, xlim = c(0,50), ylim=c(2, 6), xlab="", ylab="", yaxt="n", asp=1, xpd=TRUE)
DrawCircle(x=plotdat$xcords, y=plotdat$ycords, r.out = 2)

Drawing circles in R

As @Baptiste says above, you can use plot(...,asp=1). This will only work if your x and y ranges happen to be the same, though (because it sets the physical aspect ratio of your plot to 1). Otherwise, you probably want to use the eqscplot function from the MASS package. A similar issue arises whenever you try to do careful plots of geometric objects, e.g. Drawing non-intersecting circles

This plot is produced by substituting MASS::eqscplot for plot in your code above:

Note that depending on the details of what R thinks about your monitor configuration etc., the circle may look a bit squashed (even though it goes through the points) when you plot in R's graphics window -- it did for me -- but should look OK in the graphical output.

How to draw multiple centric circles in R

draw.circle seems to accept a vector of inputs, so use whatever function is convenient to make your sequence of inputs and pass that to the function.

plot(0,0,type = "n", xlim = c(-10,10), ylim = c(-10,10))
draw.circle (0,0,seq(0,4,.5))

How to draw a half circle on a plot?

Do you mean this?

x <- seq(0, pi, length.out = 500)
W <- 3
plot(cos(x) * W, sin(x) * W, type = "l")

plotting a circle inside a square in R

You need to specify asp=1

require(plotrix)
require(grid)

plot(c(-1, 1), c(-1,1), type = "n", asp=1)
rect( -.5, -.5, .5, .5) 
draw.circle( 0, 0, .5 )

See also: Drawing non-intersecting circles
This one got me too!

Draw circle with ggplot2 using coordinates

library(ggplot2)
library(ggforce)

dat = read.table(text="        x           y     sizes
  0.95285914  0.06596914 0.8868900
                 -1.59822942  0.71052036 2.3087498
                 0.39216559  0.58428603 0.1921204
                 0.16559318 -0.99303562 1.1586288
                 -0.43047728 -0.96649463 0.5360174
                 -0.73746484 -0.21143717 0.5260277
                 0.58779207  0.08073626 0.5070558
                 0.74936811  0.54462816 0.2047399
                 -0.01587290 -0.14835109 0.1324782
                 -0.06573365  0.33317857 0.3989122", header=TRUE)

ggplot(dat, aes(x0=x, y0=y, r=sizes)) + 
  geom_circle() + coord_equal() + theme_classic()

How to draw circles around polygon/spider chart, without plotting libraries

I don't know of any functions in base R that do circles for you, but you can concoct them manually.

center <- c(x=2.1, y=2.1) # probably a better way
half <- seq(0, pi, length.out = 51)
for (D in d1) {
  Xs <- D * cos(half); Ys <- D * sin(half)
  lines(center["x"] + Xs, center["y"] + Ys, col = "gray", xpd = NA)
  lines(center["x"] + Xs, center["y"] - Ys, col = "gray", xpd = NA)
}

Notes:

• I don't know off-hand how the center-point should be calculated, I chose that point using locator(1); not being familiar with stars, there may be a better way to determine this programmatically and more accurately;
• The first lines(.) draws the upper semi-circle; the second draws the lower.
• The xpd=NA is to preclude clipping due to the drawing margin. It may not be necessary in your "real" data. See ?par for more details on this.
• Though it may be difficult to detect here, the gray circles are drawn on top of the stars plot, which might be an aesthetic compromise. The only way around that is to plot the circles first. To do this, draw the first semicircle first with plot(..., type="l") and then add the remainder as expected, and only then run stars(..., add=TRUE).

How to draw circles inside each other with ggplot2?

The code you have with coord_polar() is correct, just the plot limits need adjusting to see both the circles, e.g.

ggplot(data) +
  geom_line(aes(x1,y1)) +
  geom_line(aes(x1,y2)) +
  coord_polar() + ylim(c(0,NA))

The reason for using ylim is that this is the direction getting transformed to the radius by the coord_polar()

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