我正在尝试在多面图中添加mean的{{1}}列。我以某种方式可以解决它，我尝试了一些功能，例如Duration Average，但是以某种方式它在多面图表上不起作用：
将此图块添加到了图表中，但是它不起作用：
geom_hline创建示例数据框：
geom_hline(yintercept= mean(`Duration Average`),
linetype="dashed",
color="black")
创建绘图的代码：
df <- structure(list(Year_Month = c(
"2016_06", "2016_06", "2016_07",
"2016_07", "2016_08", "2016_08", "2016_09", "2016_09", "2016_09",
"2016_09", "2016_10", "2016_10", "2016_10", "2016_10", "2016_11",
"2016_11", "2016_12", "2016_12", "2017_01", "2017_01", "2017_01",
"2017_02", "2017_02", "2017_02", "2017_02", "2017_03", "2017_03",
"2017_03", "2017_03", "2017_03", "2017_03", "2017_04", "2017_04",
"2017_04", "2017_04", "2017_04", "2017_05", "2017_05", "2017_05",
"2017_05", "2017_05", "2017_05", "2017_06", "2017_06", "2017_06",
"2017_06", "2017_06", "2017_06", "2017_07", "2017_07"),
Business = c("A",
"E", "A", "B", "B", "E", "F", "A", "H", "B", "A", "D", "B", "E",
"B", "E", "F", "B", "F", "B", "E", "A", "B", "C", "E", "F", "A",
"G", "D", "B", "E", "F", "A", "G", "B", "E", "F", "A", "D", "B",
"C", "E", "F", "A", "D", "B", "C", "E", "F", "A"),
`MMR Count` = c(2L,
1L, 1L, 7L, 2L, 1L, 1L, 3L, 1L, 5L, 1L, 1L, 4L, 1L, 8L, 4L, 1L,
4L, 2L, 2L, 2L, 3L, 8L, 1L, 2L, 1L, 7L, 1L, 4L, 9L, 2L, 4L, 10L,
2L, 15L, 7L, 4L, 27L, 2L, 14L, 1L, 6L, 9L, 31L, 5L, 14L, 1L,
4L, 5L, 21L),
`Duration Average` = c(37, 20, 9, 8, 2, 5, 1, 1,
1, 14, 1, 19, 8, 1, 21, 77, 1, 18, 8, 1, 1, 194, 9, 14, 19, 1,
10, 1, 6, 9, 18, 4, 12, 170, 7, 35, 9, 10, 7, 12, 3, 15, 5, 9,
10, 10, 18, 11, 16, 14)), .Names = c("Year_Month", "Business",
"MMR Count", "Duration Average"), row.names = c(NA, 50L), class = "data.frame")