How to remove the vertical asymptote using curve function in R

n <- 1e3
from <- -9
to <- 6

tol <- (to - from) / n

curve(
  ifelse(abs(x + 2) > tol, (x+3)/(x+2), NA), 
  from = from, 
  to   = to,
  n = n,
  xlab = "",
  ylab = "",
  #   xlim = ,
  ylim = c(-0.5,2.5),
  las  = 1,
  lwd  = 2
)

The reason it does that is because the "continuous" domain of x hits the most-nonzero finite y (negative) that R recognizes and then starts again at the most nonzero finite y (positive) and continues the line through those two points. The answer to this is to stop the curve immediately before that point (x = -2) and draw a second line just after that point, adding xlim= to the first call and add=TRUE to the second. (Most of the options are not needed or even used when add=TRUE, so I'll omit them here for demonstration of "simple".)

curve(
    (x+3)/(x+2), 
    from = -9, 
    to   = -2.1,
    xlab = "",
    ylab = "",
    xlim = c(-9, 6),
    ylim = c(-0.5,2.5),
    las  = 1,
    lwd  = 2
    )
curve(
    (x+3)/(x+2), 
    from = -1.9, 
    to   = 6,
    lwd  = 2,
    add = TRUE)