ggplot转plotly（ggplotly）后图例消失的问题及解决

在R环境中，使用ggplotly()将带有颜色、形状分组图例的ggplot图表转换为plotly格式时，会出现图例消失的问题。经排查，问题根源在于原ggplot代码中的guides()函数，移除该函数后，plotly图表的图例即可正常显示。以下是完整示例：

示例数据 #

library(scales)
packageVersion("ggplot2")
#> [1] '3.4.0'
library(plotly)
packageVersion("plotly")
#> [1] '4.10.1'

data <- data.frame(
  stringsAsFactors = FALSE,
  Level = c("Fast","Fast","Fast","Fast",
            "Fast","Fast","Slow","Slow","Slow",
            "Slow","Slow","Slow"),
  Period = c("1Year","3Month","1Year","3Month",
             "1Year","3Month","1Year","3Month",
             "1Year","3Month","1Year","3Month"),
  X = c(0.002,0.002,0.1,0.1,0.9,0.9,
        0.002,0.002,0.1,0.1,0.9,0.9),
  Y = c(1.38,1.29,1.61,1.61,1.74,0.98,
        1.14,0.97,1.09,1.1,0.94,0.58)
)

含guides()的原ggplot代码 #

这段代码生成的ggplot图表显示正常，但转换为plotly后图例消失：

plt <- ggplot(data = data,
             aes(x = X,
                 y = Y,
                 shape = Period,
                 color = Level)) +
  geom_point(alpha = 0.6, size = 3) +
  labs(x = " ",
       y = "Value") +
  scale_y_continuous(labels = number_format(accuracy = 0.1)) +
  guides(color = guide_legend(title = "Level", order = 1),
         shape = guide_legend(title = "Period", order = 2)) +
  theme(axis.text.x = element_text(angle = 90))
plt

转换后图例消失的plotly代码 #

运行以下代码，生成的plotly图表无图例：

ggplotly(plt, height = 500) %>%
  layout(xaxis = list(autorange = "reversed"))

修复后的代码 #

移除guides()函数后，重新生成ggplot再转换为plotly，图例即可正常显示。同时可通过layout()自定义图例标题：

plt2 <- ggplot(data = data,
             aes(x = X,
                 y = Y,
                 shape = Period,
                 color = Level)) +
  geom_point(alpha = 0.6, size = 3) +
  labs(x = " ",
       y = "Value") +
  scale_y_continuous(labels = number_format(accuracy = 0.1)) +
  theme(axis.text.x = element_text(angle = 90))
plt2

ggplotly(plt2, height = 500) %>%
  layout(
    xaxis = list(autorange = "reversed"),
    legend = list(
      title = list(text = '(Period, Level)'))
  )

内容的提问来源于stack exchange，提问作者Tung