Question

ggplot2 adjust the ylim automatically for the data points. Is there any way to adjust the ylim for stat_summary too?

df <- structure(list(Varieties = structure(c(2L, 3L, 4L, 1L, 2L, 3L,
4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L,
4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L,
4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L,
4L, 1L, 2L, 3L, 4L, 1L), .Label = c("F9917", "Hegari", "JS263",
"JS2002"), class = "factor"), Priming = structure(c(2L, 2L, 2L,
2L, 5L, 5L, 5L, 5L, 3L, 3L, 3L, 3L, 1L, 1L, 1L, 1L, 4L, 4L, 4L,
4L, 2L, 2L, 2L, 2L, 5L, 5L, 5L, 5L, 3L, 3L, 3L, 3L, 1L, 1L, 1L,
1L, 4L, 4L, 4L, 4L, 2L, 2L, 2L, 2L, 5L, 5L, 5L, 5L, 3L, 3L, 3L,
3L, 1L, 1L, 1L, 1L, 4L, 4L, 4L, 4L), .Label = c("CaCl2", "Dry",
"Hydropriming", "KNO3", "OnFarmpriming"), class = "factor"),
    PH = c(225.8, 224.26, 228.9, 215.82, 230.3, 227.7, 232.8,
    221.1, 260.2, 230.8, 236.75, 230.5, 250.56, 230.74, 240.64,
    226.7, 268.4, 233.4, 243.33, 232.7, 252.04, 233.1, 237.14,
    220.6, 265.55, 234.93, 240.04, 218.21, 300.55, 245, 243.5,
    234.65, 253.3, 233.5, 238.62, 225.93, 255.74, 233.64, 238.1,
    230.93, 246, 240.33, 246.08, 221.7, 250.54, 242.87, 251,
    225.32, 251.47, 245.4, 266.74, 227.73, 290.62, 246.68, 256.4,
    225.83, 282.67, 240.58, 258.35, 235.87)), .Names = c("Varieties",
"Priming", "PH"), class = "data.frame", row.names = c(NA, 60L
))

p1 <- ggplot(data=df, aes(x=Varieties, y=PH, group=Priming, shape=Priming, colour=Priming))+
     stat_summary(fun.y=mean, geom="point", size=2, aes(group=Priming, shape=Priming, colour=Priming))+
     theme_bw()
p1 <- p1 + stat_summary(fun.y=mean, geom="line", aes(group=Priming, shape=Priming, colour=Priming))
print(p1)

See extra space in ylim for stat_summary values. Thanks in advance for your help and time.

Answer 1

Here is one approach, using plyr to prep the data before plotting

df <- ddply(df, .(Varieties, Priming), transform, meanPH = mean(PH))
ggplot(df, aes(Varieties, meanPH)) + 
  geom_point() +
  geom_line(aes(group = Priming, color = Priming))