点线ggplot中的标记点

Question

我的数据框是

  df <- structure(list(pred_D_class = structure(1:16, .Label = c("2", 
                                                                  "6", "10", "14", "18", "22", "26", "30", "34", "38", "42", "46", 
                                                                  "50", "54", "58", "62", "66"), class = "factor"), sr = c(0.809651537358495, 
                                                                                                                           0.117375642771934, -0.363261042177462, -0.108072060684085, 0.317179663964105, 
                                                                                                                           0.580775326984562, -0.264034203498261, -1.33324816316546, -1.62553076157225, 
                                                                                                                           -1.41389979866552, 1.88153232792938, 5.27111236575782, 6.54991048921335, 
                                                                                                                           8.45749771079771, 6.59078999361768, 16.5363599853556), sr1 = c(-0.461973610529103, 
                                                                                                                                                                                          -0.632872471230115, -0.615633624705446, 0.191948419914372, 0.724674733712783, 
                                                                                                                                                                                          0.856251476967346, -0.255899968913292, -2.60345961297358, -4.17467513135888, 
                                                                                                                                                                                          -5.40431493394634, -4.50433525555663, -3.77830406394879, -6.17234432719018, 
                                                                                                                                                                                          -6.82309808877181, -13.2855824994648, -7.88630469512728), sr2 = c(1.5034529269785, 
                                                                                                                                                                                                                                                            1.50797890743077, 0.522711463953773, 0.0884734945633313, -0.0740798054484882, 
                                                                                                                                                                                                                                                            -0.0134157046284108, -1.0261643625092, -2.22477319635843, -2.2938676440796, 
                                                                                                                                                                                                                                                            -2.48543981495454, -1.89315257576394, -2.35142885487948, -2.57245688973948, 
                                                                                                                                                                                                                                                            -1.9149000167909, -4.97513391133261, 4.42059763647021), co = c(25L, 
                                                                                                                                                                                                                                                                                                                           1580L, 5579L, 10895L, 9520L, 5091L, 3084L, 1681L, 1055L, 609L, 
                                                                                                                                                                                                                                                                                                                           270L, 133L, 61L, 19L, 1L, 1L)), .Names = c("pred_D_class", "sr", 
                                                                                                                                                                                                                                                                                                                                                                      "sr1", "sr2", "co"), row.names = c(NA, -16L), class = c("tbl_df", 
                                                                                                                                                                                                                                                                                                                                                                                                                              "tbl", "data.frame"), drop = TRUE)

对于这个data.frame，我会关注ggplot

library(reshape2)
df1 <- subset(melt(df), variable != "co")
library(ggplot2)
ggplot(aes(x = pred_D_class, y = value, group = variable, color = variable), data = rez1) + geom_point() + geom_line()

这给出了以下情节

我想现在添加代表co中的列df data.frame的标签，并且对于所有组sr, sr1, sr2都是通用的。此值可以放在y = 15中，也可以放在红线后面。 到目前为止，我尝试了与geom_text, geom_label和annotate的不同组合，但没有成功。