r - 在scale_*_manual中使用palette参数

Question

背景

?scale_fill_manual 的帮助说:

 ...: Arguments passed on to ‘discrete_scale’
          palette A palette function that when called with a single
              integer argument (the number of levels in the scale)
              returns the values that they should take.

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代码

因此，我尝试了:

library(ggplot)
library(dplyr)

my_pal <- colorRampPalette(1:3)

(p <- ggplot(mtcars %>% 
              group_by(cyl) %>% 
              summarise(mpg = mean(mpg)), 
             aes(x = factor(cyl), y = mpg, fill = factor(cyl))) +
   geom_col())

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问题

但是如果我想将调色板功能添加到比例中，它就不起作用:

p + scale_fill_manual(palette = my_pal)
# Error in as.vector(x, "character") : 
#   cannot coerce type 'closure' to vector of type 'character'

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问题

如何正确使用palette参数？我知道如何正确设置颜色，但我想了解 palette 参数的用途以及如何使用它。如果它是一个内部参数，我想知道为什么它首先在 scale_*_manual API 中可用。

Answer 1

这似乎是一个错误。请参阅(已关闭)问题:scale_colour_manual(palette=foo): cannot coerce type 'closure' to vector of type 'character' :

@sjackman:

How is the palette argument meant to be used; is there an example in the documentation?

@克劳斯威尔克:

It's not meant to be used at all. The bug is that palette is accessible and mentioned in the documentation.