set.seed(97536917)
x <- rnorm(100)
y <- x+rnorm(100, 0, 0.7)
grayplot(x, y, col="slateblue", pch=16)
at <- seq(-3, 3)
grayplot(x, y, col="violetred", pch=16, hlines=at, vlines=at)
grayplot(x, col="Orchid", pch=16, bgcolor="gray80",
hlines=seq(-4, 4, by=0.5), hlines.lwd=c(3,1),
vlines=seq(0, 100, by=5), vlines.lwd=c(3,1,1,1))
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