根据ggplot2中的聚合数据放置线性线

dput(x)
structure(list(Date = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 
2L, 3L, 3L, 3L, 3L), .Label = c("1/1/2012", "2/1/2012", "3/1/2012"
), class = "factor"), Server = structure(c(1L, 2L, 3L, 4L, 1L, 
2L, 3L, 4L, 1L, 2L, 3L, 4L), .Label = c("A", "B", "C", "D"), class = "factor"), 
    Storage = c(10000L, 20000L, 30000L, 15000L, 15000L, 25000L, 
    35000L, 15700L, 16000L, 27000L, 37000L, 16700L)), .Names = c("Date", 
"Server", "Storage"), class = "data.frame", row.names = c(NA, 
-12L))
dput(x)
structure(list(Date = structure(c(1L, 1