The meaning of Warning message: Removed 4 rows containing missing values (geom_path)

Question

Data : https://drive.google.com/file/d/0B20HmmYd0lsFSmZhYUk3bkRTNFk/edit?usp=sharing

plot.df<- read.table("meansses.txt")

theme_luke <- function (base_size = 12, base_family = "") {
theme_gray(base_size = base_size, base_family = base_family) %+replace% 
theme(
  panel.background = element_rect(fill="white"),
  panel.grid.minor.y = element_blank(),
  legend.key = element_rect(fill="white", colour= "white"),
  strip.background = element_rect(fill="white")
)   
}
theme_set(theme_luke())

ggplot(plot.df, aes(factor(L2),mean)) + 
 geom_point(stat = "identity",aes(shape=L3), size=4, group=L3) +
 scale_shape(solid = FALSE) +
 geom_errorbar(aes(ymax = mean + se, ymin = mean - se)) +
 facet_grid(. ~ L1) +
 xlab("Levels") + ylab("Proportion") +
 ylim(0,0.12)

It all works fine except when I set ylim I get

Warning message:
Removed 4 rows containing missing values (geom_path) .

Can somebody explain to me what that means in this context?

Answer 1

The warning means that some elements are removed because they fall out of the specified range. In your case, all points are inside the range, but one error bar is not.