条形图的误差条仅在一个方向，但最后一个在相反方向

Question

这个很有用post shows how to display error bars in one direction only with ggplot. To do this, the geom_errorbar function is modified as follows (as proposed by Sean Hughes):

geom_uperrorbar <- function(mapping = NULL, data = NULL,
   stat = "identity", position = "identity",
   ...,
   na.rm = FALSE,
   show.legend = NA,
   inherit.aes = TRUE) {
   layer(
      data = data,
      mapping = mapping,
      stat = stat,
      geom = GeomUperrorbar,
      position = position,
      show.legend = show.legend,
      inherit.aes = inherit.aes,
      params = list(
         na.rm = na.rm,
         ...
      )
   )
}

GeomUperrorbar <- ggproto("GeomUperrorbar", Geom,
   default_aes = aes(colour = "black", size = 0.5, linetype = 1, width = 0.5,
      alpha = NA),

   draw_key = draw_key_path,
required_aes = c("x", "y", "ymax"),

   setup_data = function(data, params) {
      data$width <- data$width %||%
         params$width %||% (resolution(data$x, FALSE) * 0.9)

      transform(data,
         xmin = x - width / 2, xmax = x + width / 2, width = NULL
      )
   },draw_panel = function(data, panel_scales, coord, width = NULL) {
      GeomPath$draw_panel(data.frame(
         x = as.vector(rbind(data$xmin, data$xmax, NA, data$x,   data$x)),
         y = as.vector(rbind(data$ymax, data$ymax, NA, data$ymax, data$y)),
         colour = rep(data$colour, each = 5),
         alpha = rep(data$alpha, each = 5),
         size = rep(data$size, each = 5),
         linetype = rep(data$linetype, each = 5),
         group = rep(1:(nrow(data)), each = 5),
         stringsAsFactors = FALSE,
         row.names = 1:(nrow(data) * 5)
      ), panel_scales, coord)
   }
)


"%||%" <- function(a, b) {
   if (!is.null(a)) a else b
}

但现在我遇到了最后一根柱线为负的情况。因此，最后一个柱的误差柱必须朝另一个方向移动。有谁知道这是如何工作的？

这是一个可重现的例子：

df <- data.frame(trt = factor(c(1, 1, 2, 2)), resp = c(1, 5, 3, -2),
                 group = factor(c(1, 2, 1, 2)), se = c(0.1, 0.3, 0.3, 0.2))
df2 <- df[c(1,3), ]

limits <- aes(ymax = resp + se, ymin = resp - se)
dodge <- position_dodge(width = 0.9)

p <- ggplot(df, aes(fill = group, y = resp, x = trt))
p + geom_bar(position = dodge, stat = "identity") +
  geom_errorbar(limits, position = dodge, width = 0.25)

Answer 1

链接问题中的解决方案实际上会产生这个结果。您只需要确保在条形向下时减去而不是添加标准误差：

limits <- aes(ymax = resp + se * sign(resp))

现在您的绘图代码几乎没有改变：

dodge  <- position_dodge(width = 0.9)

ggplot(df, aes(fill = group, y = resp, x = trt)) +
  geom_bar(position = dodge, stat = "identity") +
  geom_uperrorbar(limits, position = dodge, width = 0.25)

条形图的误差条仅在一个方向，但最后一个在相反方向

Error bars for barplot only in one direction, but for the last one in the opposite direction

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