R ggplot2中的颜色错误条

对于示例数据帧：

df <- structure(list(site = structure(c(1L, 1L, 1L, 1L, 3L, 3L, 3L, 
                                         3L, 3L, 4L, 4L, 4L, 4L, 5L, 5L, 5L, 2L, 2L, 2L, 2L), .Label = c("1 - JL", 
                                                                                                         "11 - KT", "2 - SSD", "3 - USSD", "4 - MES"), class = "factor"), 
                      x = c(3L, 4L, 2L, 2L, 4L, 6L, 1L, 3L, 6L, 4L, 4L, 5L, 3L, 
                            3L, 3L, 1L, 2L, 5L, 4L, 1L), y = c(3L, 5L, 3L, 5L, 4L, 3L, 
                                                               5L, 2L, 6L, 4L, 3L, 5L, 5L, 5L, 6L, 3L, 4L, 3L, 4L, 2L), 
                      type = structure(c(1L, 2L, 3L, 4L, 1L, 2L, 3L, 3L, 4L, 3L, 
                                         3L, 3L, 1L, 2L, 2L, 2L, 2L, 1L, 1L, 1L), .Label = c("a", 
                                                                                             "b", "c", "d"), class = "factor"), y_upper.error = c(2L, 
                                                                                                                                                  4L, 2L, 4L, 3L, 2L, 4L, 1L, 5L, 3L, 2L, 4L, 4L, 4L, 5L, 2L, 
                                                                                                                                                  3L, 2L, 3L, 1L), y_lower.error = c(4.5, 6.5, 4.5, 6.5, 5.5, 
                                                                                                                                                                                     4.5, 6.5, 3.5, 7.5, 5.5, 4.5, 6.5, 6.5, 6.5, 7.5, 4.5, 5.5, 
                                                                                                                                                                                     4.5, 5.5, 3.5)), .Names = c("site", "x", "y", "type", "y_upper.error", 
                                                                                                                                                                                                                 "y_lower.error"), class = "data.frame", row.names = c(NA, -20L
                                                                                                                                                                                                                 ))

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df这是一个黑客解决方案，它将错误条分成两部分（从下尾端到y，从y到上尾端）并分别着色：

ggplot(df2, aes(x=x, y=y, shape = type))+
  geom_errorbar(aes(ymin=y, ymax=y_upper.error), colour="blue", width = 0.1) +
  geom_errorbar(aes(ymin=y_lower.error, ymax=y), colour="red", width = 0.1) +
  geom_point() +
  scale_shape_manual(values=c(21,15,25,18)) + #makes open circle/triangle
  facet_wrap(~site, ncol=2)


我缩短了错误条尾部的宽度，以便它们（大约）被
geom_点
覆盖

ggplot(df2, aes(x=x, y=y, shape = type))+
  geom_errorbar(aes(ymin=y, ymax=y_upper.error), colour="blue", width = 0.1) +
  geom_errorbar(aes(ymin=y_lower.error, ymax=y), colour="red", width = 0.1) +
  geom_point() +
  scale_shape_manual(values=c(21,15,25,18)) + #makes open circle/triangle
  facet_wrap(~site, ncol=2)