plot(0,0,
     xlim = c(0,10),
     ylim = c(0,6),
     asp = 1, ## units are of equal length on the two axis
     xlab = "Risk ratio",
     ylab = "Odds ratio",
     type = "n",
     yaxp = c(0,6,3)
     )
abline(0,1, lty="dashed")
 for (p in seq(0.02, 0.2, 0.02)){
   curve((1/p - 1)/(1/p - x)*x, 1, 1/p, add=TRUE)
}