Plot kobe

# S3 method for kobe
plot(vpares, Bref, Uref, plot.history = FALSE,
  is.plot = FALSE, pickU = "", pickB = "", ylab.tmp = "U/Umsy",
  xlab.tmp = "SSB/SSBmsy", title.tmp = "")

# S3 method for kobemat
plot(xx, title.name = "", line = 0)