如何在 R 中反转颜色条的方向？

Question

我使用plotly 的R 接口用颜色条进行绘制，它将连续变量映射到颜色渐变。通过 debault，plotly 将最小值放在颜色栏的底部，将最大值放在颜色栏的顶部。如图所示。

现在我想反转整个颜色条，最小值在顶部。但是，我还没有找到（或者我错过了）实现我的目标的选项。有什么办法可以反转颜色条吗？

---

感谢@vestland 提供以下示例代码：

library(plotly)
df <- read.csv("https://raw.githubusercontent.com/plotly/datasets/master/2011_us_ag_exports.csv")
df$hover <- with(df, paste(state, '<br>', "Beef", beef, "Dairy", dairy, "<br>",
                           "Fruits", total.fruits, "Veggies", total.veggies,
                           "<br>", "Wheat", wheat, "Corn", corn))
# give state boundaries a white border
l <- list(color = toRGB("white"), width = 2)
# specify some map projection/options
g <- list(
  scope = 'usa',
  projection = list(type = 'albers usa'),
  showlakes = TRUE,
  lakecolor = toRGB('white')
)

fig <- plot_geo(df, locationmode = 'USA-states', reversescale = T)
fig <- fig %>% add_trace(
    z = ~total.exports, text = ~hover, locations = ~code,
    color = ~total.exports, colors = 'Purples'
  )
fig <- fig %>% colorbar(title = "Millions USD")
fig <- fig %>% layout(
    title = '2011 US Agriculture Exports by State<br>(Hover for breakdown)',
    geo = g
  )

fig

参数reversescale 反转值和颜色之间的映射。但是，我的目标是反转整个颜色条（不更改映射）。在我的例子中，将值 1 放在颜色条的顶部，将最大值放在底部更合理，因为这些值是某个指标的排名。

---

纯ggplot 的类似问题。我刚刚发现我也无法反转ggplot 中的颜色条。

Answer 1

看起来您正在使用plot_geo()。在这种情况下，只需像这样包含reversescale = T：

plot_geo(df, locationmode = 'USA-states', reversescale = T)`

这对于使用颜色条的大多数其他功能也应该有效。

情节 1：reversescale = F 或未指定

情节2：reversescale = T

完整代码：

library(plotly)
df <- read.csv("https://raw.githubusercontent.com/plotly/datasets/master/2011_us_ag_exports.csv")
df$hover <- with(df, paste(state, '<br>', "Beef", beef, "Dairy", dairy, "<br>",
                           "Fruits", total.fruits, "Veggies", total.veggies,
                           "<br>", "Wheat", wheat, "Corn", corn))
# give state boundaries a white border
l <- list(color = toRGB("white"), width = 2)
# specify some map projection/options
g <- list(
  scope = 'usa',
  projection = list(type = 'albers usa'),
  showlakes = TRUE,
  lakecolor = toRGB('white')
)

fig <- plot_geo(df, locationmode = 'USA-states', reversescale = T)
fig <- fig %>% add_trace(
    z = ~total.exports, text = ~hover, locations = ~code,
    color = ~total.exports, colors = 'Purples'
  )
fig <- fig %>% colorbar(title = "Millions USD")
fig <- fig %>% layout(
    title = '2011 US Agriculture Exports by State<br>(Hover for breakdown)',
    geo = g
  )

fig