month   Yi      Yi+1
1   0.014310185 13.43838262
2   0.014310185 15.7792948
3   0.176113783 16.14479846
4   3.143663699 16.54060078
5   3.755478277 16.75810501
6   3.767263653 17.03156884
7   3.767263653 17.03156884
8   3.829219647 17.03156884
9   4.375269901 17.78482322
10  8.707536696 18.47995179
11  10.28741362 21.33942187
12  10.66218286 21.82637774

df  <- read_excel("df.xls", col_names = FALSE, skip = 1)
colnames(df) <- c("month", "Yi","Yi+1", "Yi+2", "Yi+3", "Yi+4", "Yi+5","Yi+6",  "Yi+7", "Yi+8", "Yi+9", "Yi+10","Yi+11","Yi+12","Yi+13","Yi+14")

df.melt <- melt(tab.df, id = c("month","Yi","Yi+1","Yi+2",  "Yi+3", "Yi+4", "Yi+5","Yi+6",  "Yi+7", "Yi+8", "Yi+9", "Yi+10","Yi+11","Yi+12","Yi+13",    "Yi+14"))

bar <- group_by(df.melt, vars = c(1:12), drop = "month")

ggplot(bar, aes(x=variable, y=mean, fill=factor(month)))+

geom_bar(position="dodge", stat="identity")