单独缩放 ggplot 的极坐标图中的轴？

Question

我的数据集是

cvar setting value
var1 min 20
var2 min 5
var3 min 140
var4 min 40
var5 min 600
var1 max 60
var2 max 15
var3 max 180
var4 max 80
var5 max 1200
var1 center 40
var2 center 10
var3 center 160
var4 center 60
var5 center 900
var1 upper 57
var2 upper 13
var3 upper 162
var4 upper 79
var5 upper 1250
var1 lower 20
var2 lower 6
var3 lower 153
var4 lower 40
var5 lower 620

有

library(ggplot2)
ggplot(data=daten, aes(x=factor(cvar), y=value, group = setting, color = setting)) + 
  geom_line() + 
  coord_polar()

我得到了接近我正在寻找的东西。我想单独缩放每个轴，从 0 到相应的最大值，或者每个轴都有单独的最小值和最大值。

有人可以给我提示吗？提前致谢霍尔格

Answer 1

如果你的意思是你想为每个 cvar 缩放值的范围，你可以在将数据框传递给 ggplot 之前这样做：

library(dplyr)

daten2 <- daten %>%
  group_by(cvar) %>%

  # option 1: this scales the values at each varX from 0 to max
  mutate(value.scaled = value / max(value)) %>% 

  # option 2: this scales the values at each varX from min to max
  mutate(value.scaled2 = (value - min(value)) / (max(value) - min(value))) %>%

  ungroup() %>%
  mutate(setting = factor(setting,
                          levels = c("max", "upper", "center", "lower", "min")))

p1 <- ggplot(data = daten2, 
       aes(x = factor(cvar), y = value.scaled, group = setting, color = setting)) + 
  geom_line(size = 1) + 
  expand_limits(y = 0) +
  coord_polar() +
  ggtitle("Scaled value range from 0 to max")

p2 <- ggplot(data = daten2, 
             aes(x = factor(cvar), y = value.scaled2, group = setting, color = setting)) + 
  geom_line(size = 1) + 
  coord_polar() +
  ggtitle("Scaled value range from min to max")

gridExtra::grid.arrange(p1, p2, nrow = 1)

编辑：如果要加入第一个和最后一个cvar值，可以在x轴的末尾重复var1，显式设置expand = c(0, 0) 以便最后一个 cvar 值与极坐标下的第一个值连接起来：

# I'm only demonstrating with one of the two cases above, 
# but the same principle applies in either case.

ggplot(data = daten2 %>%
         filter(cvar == "var1") %>% # make a copy of the dataset with only var1
         mutate(cvar = "var6") %>%
         rbind(daten2),             # append the copy to the full dataset
             aes(x = factor(cvar), y = value.scaled2, group = setting, color = setting)) + 
  geom_line(size = 1) + 
  scale_x_discrete(expand = c(0, 0),
                   breaks = c("var1", "var2", "var3", "var4", "var5")) +
  coord_polar() +
  ggtitle("Scaled value range from min to max")

如果您希望直线在极坐标下是直的，答案描述了另一种选择：

coord_radar <- function (theta = "x", start = 0, direction = 1) {
  theta <- match.arg(theta, c("x", "y"))
  r <- if (theta == "x") "y" else "x"
  ggproto("CordRadar", CoordPolar, theta = theta, r = r, start = start, 
          direction = sign(direction),
          is_linear = function(coord) TRUE)
}

ggplot(data = daten2 %>%
         filter(cvar == "var1") %>%
         mutate(cvar = "var6") %>%
         rbind(daten2), 
             aes(x = factor(cvar), y = value.scaled2, group = setting, color = setting)) + 
  geom_line(size = 1) + 
  scale_x_discrete(expand = c(0, 0),
                   breaks = c("var1", "var2", "var3", "var4", "var5")) +
  coord_radar() +
  ggtitle("Scaled value range from min to max")

单独缩放 ggplot 的极坐标图中的轴？

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