error bar for within-subject design

errorbars.r

library(reshape2)
library(ggplot2)

set.seed(42)
v1 <- rnorm(20, 0, 20)
v2 <- v1 + 0.1 + rnorm(20, 0, 0.1)
df1 <- melt(data.frame(v1, v2))
TT1 <- t.test(value ~ variable, data = df1, paired = TRUE)

v1 <- rnorm(20, 0, 10)
v2 <- v1 + 2 + rnorm(20, 0, 10)
df2 <- melt(data.frame(v1, v2))
TT2 <- t.test(value ~ variable, data = df2, paired = TRUE)

df1$g <- 1
df2$g <- 2
df <- rbind(df1, df2)

ggplot(df, aes(variable, value)) + 
  stat_summary(fun.data = mean_se) +
  facet_grid(.~g, labeller = function(x, y) 
    ifelse(y == "1", format(TT1$p.value), format(TT2$p.value)))

TT1
TT2

ggplot(df, aes(variable, value)) + 
  stat_summary(fun.data = mean_se) +
  facet_grid(.~g, labeller = function(x, y) 
    ifelse(y == "1", format(TT1$p.value), format(TT2$p.value))) +
  geom_point() + geom_line(aes(group = 1:20))
  

t.test(value ~ variable, data = df1, paired = FALSE)
t.test(value ~ variable, data = df2, paired = FALSE)