Problems with line types in plots saved as PDF files

Hi,

I am trying to save a plot as a PDF with different line types. In the example below, R displays the plot correctly with 2 curves in solid lines, 2 curves in dashed lines and 1 curve as a dotted line. However, when I save the image as PDF (as attached), the dashed lines become solid.

Is there any way around this? Saving the image as a JPEG or PNG file works fine but the image quality is not desirable.

b.hat = 6
a.1 = -12
a.2 = 0
a.3 = 200

b = seq(-10, 10, 0.0002)
l = a.1*(b - b.hat)^2 + a.2*(b - b.hat) + a.3

lambda = 20

p = -lambda*abs(b)

pen.like = l + p

y.min = 3*min(p)
y.max = max(c(l, p, pen.like))

#pdf(file = "TestPlot.pdf", 6, 6)
#{
plot(b, l, type = "l", ylim = c(y.min, y.max), lwd = 2, xlab = expression(beta), ylab = "", col = "green", yaxt = "n", xaxt = "n")
points(b, p, type = "l", lty = "dotted", lwd = 2, col = "red")
points(b, pen.like, type = "l", lwd = 2, lty = "dashed", col = "green")

axis(1, at = c(0))
axis(2, at = c(0))

lambda.hat = which.max(pen.like)
lambda.glm = which(b == b.hat)

points(b[lambda.glm], l[lambda.glm], pch = 16, cex = 1.5)
points(b[lambda.hat], l[lambda.hat], pch = 17, cex = 1.5)

b.hat = -3
a.1 = -1.5
a.2 = 0
a.3 = 120

l = a.1*(b - b.hat)^2 + a.2*(b - b.hat) + a.3

pen.like = l + p

points(b, l, type = "l", lwd = 2, col = "blue")
points(b, pen.like, type = "l", lwd = 2, lty = "dashed", col = "blue")

lambda.hat = which.max(pen.like)
lambda.glm = which(b == b.hat)

points(b[lambda.glm], l[lambda.glm], pch = 16, cex = 1.5)
points(b[lambda.hat], l[lambda.hat], pch = 17, cex = 1.5)

abline(h = 0)
abline(v = 0)

#}

#dev.off()


Thanks,

Ian