R ggplot：为连续变量R95p_e设置点大小分档的问题

1. 连续变量分档失败 #

想要给连续变量R95p_e分档，用来控制散点图的点大小，执行以下代码：

iris <- iris %>% mutate(discrete_var2 = cut(R95p_e, c(-0.5,0.06,0.08,0.1,0.12,0.14,0.16,0.18,0.2,3))))

报错信息：Error: Continuous value supplied to discrete scale，尝试将R95p_e转为数值型或因子型后仍无法解决。

2. 散点图点大小完全一致 #

改用直接映射连续变量R95p_e到点大小的代码，结果所有点大小无差异：

iris %>% 
  ggplot(aes(CDD_d, R95p_d, color = discrete_var, size = R95p_e)) +
  geom_quadrant_lines(linetype = "solid") +
  geom_point(alpha = 0.5) +
  scale_color_manual(values = col) +
  scale_size_continuous(breaks = c(1,2,3,4,5,6,7,8)) +
  scale_x_continuous(limits = symmetric_limits) +
  scale_y_continuous(limits = symmetric_limits) +
  theme_minimal() + 
  geom_text(aes(label = ifelse(CDD_e > quantile(CDD_e,probs = .95,na.rm=TRUE) | R95p_e > quantile(R95p_e,probs = .95,na.rm=TRUE), as.character(NAME), ""), size = 0.1),show_guide=F) +
  labs(size="极端降水贸易加权暴露度", colour="极端干旱贸易加权暴露度")

可复现代码 #

iris <- structure(list(NAME = c("阿富汗", "阿尔巴尼亚", "阿尔及利亚", 
"美属萨摩亚", "安道尔", "安哥拉", "安圭拉", "南极洲", 
"安提瓜和巴布达", "阿根廷"), CDD_d = c(-0.0409, 0.0349, 
0.092, NA, 0.0493, -0.087, NA, NA, NA, -0.0199), R95p_d = c(0.2219, 
0.0564, 0.1601, NA, 0.0669, 1.9369, NA, NA, NA, 0.124), CDD_e = c(0.0163842166664955, 
0.0420785596173385, 0.0301859613207384, NA, NA, 0.0132801284765419, 
NA, NA, 0.01446, 0.0979854033169376), R95p_e = c(0.200947581296687, 
0.105155138501437, 0.123916523483283, NA, NA, 0.185846581581744, 
NA, NA, 0.01664, 0.146239802993381), discrete_var = structure(c(5L, 
7L, 6L, NA, NA, 5L, NA, NA, 5L, 9L), levels = c("— -6", "-6 to -4", 
"-4 to -2", "-2 to 0", "0 to 2", "2 to 4", "4 to 6", "6 to 8", 
"8 — "), class = "factor"), discrete_var2 = structure(c(9L, 
4L, 5L, NA, NA, 8L, NA, NA, 1L, 6L), levels = c(" — -6", "6 to 8", 
"8 to 10", "10 to 12", "12 to 14", "14 to 16", "16 to 18", "18 to 20", 
"20 —"), class = "factor")), row.names = c(NA, 10L), class = "data.frame")

内容的提问来源于stack exchange，提问作者MoonS