I am embarrassed to ask this simple question, but has been in kicking my mind for several days whenever I create a plot:
plot (x = 1:10, y = rnorm (10, 5, 2)
For posterity, here is the long-winded way of doing it manually:
plot (x = 1:10, y = rnorm (10, 5, 2))
grid (lty = 6, col = "cornsilk2")
xaxp <- par("xaxp")
yaxp <- par("yaxp")
abline(v=seq(xaxp[1], xaxp[2], (xaxp[2]-xaxp[1])/xaxp[3]), lty=6, col = "cornsilk2")
abline(h=seq(yaxp[1], yaxp[2], (yaxp[2]-yaxp[1])/yaxp[3]), lty=6, col = "cornsilk2")