regression line on boxplots

boxplot(c(1:3),c(4:6),c(5:8))

df <- structure(list(grp = c(1, 1, 1, 2, 2, 2, 3, 3, 3, 3),
   val = c(1L, 2L, 3L, 4L, 5L, 6L, 5L, 6L, 7L, 8L)),
  .Names = c("grp", "val"),
  row.names = c(NA, -10L),
  class = "data.frame")

  boxplot(val~grp,data=df)
  lm(val~grp, data=df)

#Call:
#lm(formula = val ~ grp, data = df)

#Coefficients:
#(Intercept)          grp
#    0.04348      2.21739

  ?abline
  abline(reg=lm(val~grp, data=df) )

David Winsemius, MD
West Hartford, CT