## Just for Fun: Using R to Create Targets

Submitted by dylan on Tue, 2010-08-10 17:54.

OK, not really science or soil-related, but a fun 5 minute use of R to make something you can use to improve your hand-eye coordination. Demonstrates several ways to use base graphics, user-defined functions, and calling functions from within other functions.

Implementation

# function to make the target
f.target <- function(xy, s)
{
plot(0, 0, type='n', axes=FALSE, xlab='', ylab='', xlim=c(-1,1), ylim=c(-1,1))
grid(nx=50, ny=50, lty=1)
abline(h=0, v=0, lwd=2)
f.bullseye(list(x=0,y=0), s)
f.bullseye(xy, s/2)
}

# function to make each bull's eye
f.bullseye <- function(xy, s)
{
sapply(s, function(s_i) {
points(xy, cex=s_i, lwd=2) } )
}

# concentric circle sizes
s <- c(2,8,16,24,32)
# coordinates for bull's eye marks in each quadrant
xy <- expand.grid(x=c(-0.66, 0.66), y=c(-0.66, 0.66))

# save 2x2 figure to PDF
pdf(file='target_2x2.pdf', width=11, height=8.5)
par(mfcol=c(2,2), mar=c(1,1,1,1))
for(i in 1:4) f.target(xy, s)
dev.off()

# save 2x1 figure to PDF
pdf(file='target_2x1.pdf', width=8.5, height=11)
par(mfcol=c(2,1), mar=c(1,1,1,1))
for(i in 1:2) f.target(xy, s)
dev.off()