alpha不会更改透明度，而是使用geom_rect添加到ggplot2图例

Question

我有以下数据集：

dput（ByStationR90Data [1：5，]）

structure(list(Station = structure(c(1L, 1L, 1L, 1L, 1L), .Label = c("125", 
"137"), class = "factor"), SampleDate = structure(c(13216, 13313, 
13342, 13397, 13488), class = "Date"), Date = c(20060309, 20060614, 
20060713, 20060906, 20061206), FecalColiform = c(2, 2, 79, 2, 
2), Flog = c(0.301029995663981, 0.301029995663981, 1.89762709129044, 
0.301029995663981, 0.301029995663981), Avlog = c(NA_real_, NA_real_, 
NA_real_, NA_real_, NA_real_), STD = c(NA_real_, NA_real_, NA_real_, 
NA_real_, NA_real_), F90 = c(NA_real_, NA_real_, NA_real_, NA_real_, 
NA_real_)), .Names = c("Station", "SampleDate", "Date", "FecalColiform", 
"Flog", "Avlog", "STD", "F90"), class = c("grouped_df", "tbl_df", 
"tbl", "data.frame"), row.names = c(NA, -5L), vars = list(Station), drop = TRUE, indices = list(
0:4), group_sizes = 5L, biggest_group_size = 5L, labels = structure(list(
Station = structure(1L, .Label = c("125", "137"), class = "factor")), class = "data.frame", row.names = c(NA, 
-1L), vars = list(Station), drop = TRUE, .Names = "Station"))

我创建了一个图表，显示了两个海水采样站粪便大肠菌群的第90个百分位数。 我想演示使站点处于“威胁”状态（30-43）的值范围。 我差不多了！ 我使用geom_rect创建了一个盒子，并使其带有标签的红色。 我只想使其有些透明，因为红色原样不堪重负。 每次我向方程式添加alpha时，它都不会更改红色，而是在图例上方添加一个怪异的框。 阅读过alpha的其他问题后，我尝试将其移动到其他位置，并在括号内移动，这样我会得到错误或看起来更糟的东西。

我的代码：

ThreatSt <- ggplot(subset(ByStationR90Data, Station %in% c("125", "137"))) +
    geom_hline(yintercept = 43, color = "red", linetype="dashed", size = .7, show_guide = TRUE) +
    geom_rect(mapping = aes(xmin = as.Date(c('2010-10-01')), xmax = as.Date(c('2016-04-01')), 
        ymax = 43, ymin = 30, fill = "Threatened Zone", show_guide = FALSE)) +
    scale_fill_manual("", breaks = "Threatened Zone", values = "red", alpha =  0.5)+
    geom_line(aes(SampleDate, F90, group = Station, colour = Station), size=1.5) +
    scale_color_brewer(palette = "Dark2")

ThreatSt <- ThreatSt +
    theme_bw() +
    ggtitle("Fecal Coliform Rolling 90th Percentiles for Stations 125 and 137
      \n Hood Canal #3 Growing Area") +
    ylab("Fecal Coliform (fc/100 ml)") +
    annotate(geom="text", x=as.Date("2015-01-01"), y=45,label="NSSP Limit", color="red") +
    scale_y_continuous(breaks=seq(0,100,10), limits = c(10,60)) +
    scale_x_date( 
    limits = as.Date(c('2011-01-01', '2016-01-01')), 
    labels=(c("2011", "2012", "2013", "2014", "2015", "2016")))

任何见解和/或帮助表示赞赏。 谢谢！

Answer 1

我使用模拟数据集提出以下解决方案

df <- data.frame(SampleDate = c(1,2,3,1,2,3),
                 Station = c("A","A","A","B","B","B"),
                 R90 = c(90,95,100,85,100,120))
 library(ggplot2)
ggplot(data = df) +
  geom_line(aes(x = SampleDate, y = R90, group = Station, color = Station), size = 1.5) +
  geom_rect(aes(fill = "Threatened Zone"), xmin = -Inf, xmax = +Inf,
            ymin = 95, ymax = 105, alpha = .125) +
  scale_fill_manual(breaks = "Threatened Zone", values = "red",
                    guide = guide_legend(title = "Threatened Zone",
                                         override.aes = list(alpha = .5)))

我还不明白为什么覆盖alpha时需要使用.5而不是.125的值。 （我仍在调查此问题...）