我想将出现在右侧y轴上的面标签添加到不是面的ggplot。有没有一个简单的方法来做到这一点？Plotv2显示了我想要添加的y轴标签，但实际上我并不想将数据拆分到两个方面。是否有设置的主题参数，可以用来添加第二个y轴标题容易，或者我必须去使用自定义grob？

library(ggplot2)
library(grid)
df <- data.frame(
  Position=(c(1:5000)),
  Signal=(c((rep(c(5),times=2000)), (rep(c(100),times=1000)), (rep(c(5),times=2000))))
)
Plotv1 <- ggplot() +
  geom_line(data = df, aes(x=Position, y=Signal, col = "#000000")) +
  coord_cartesian(clip="off") +
  guides(fill = "none") +
  guides(color=guide_legend(title="MyLegend")) +
  theme_bw() +
  theme(axis.text.x = element_blank()) +
  theme(
    axis.title.x = element_text(margin=margin(t=30)),
    legend.title = element_text(colour = "#000000", size=12),
    legend.text = element_text(colour = "#000000", size=12)
  ) +
  annotation_custom(
    grid::segmentsGrob(
      y0 = unit(-25, "pt"),
      y1 = unit(-25, "pt"),
      arrow = arrow(angle=45, type="closed", length=unit(.15, 'cm')),
      gp = grid::gpar(lwd=3, col="#000000", fill="#000000")
    ),
    xmin = 2000,
    xmax = 3000
  )
ggsave(paste("~/Desktop/Plotv1.png", sep = ""), Plotv1, width = 8, height = 1.7)
Plotv2 <- Plotv1 +
  facet_grid(Signal~.)
ggsave(paste("~/Desktop/Plotv2.png", sep = ""), Plotv2, width = 8, height = 1.7)