强制ggplot图例在不存在任何值时显示所有类别 [英] Force ggplot legend to show all categories when no values are present

问题描述

在下面的重现示例中，我试图强制ggplot显示图例并修复因素的颜色，即使范围中没有值。图1在变量X1的每个范围内具有至少一个值，并且根据需要绘制图。绘制每个图例标签并匹配所需的颜色。

在示例2中，变量Y1在每个创建的范围中都没有值。因此，该图仅显示前4个图例标签，并使用前4种颜色。

有没有方法可以绘制这个图形，以便强制ggplot显示所有八个传说标签和修正颜色，以便cat1值始终为红色，cat2值始终为蓝色等。

我尝试了所有我能想到但没有成功的事情。 p>

- 可复制的例子 -

  set.seed（45678）
 dat < -  data.frame（Row = rep（x = LETTERS [1：5]，times = 10），
 Col = rep（x = LETTERS [1:10]，each = 5） ，
 Y = rnorm（n = 50，mean = 0，sd = 0.5），
 X = rnorm（n = 50，mean = 0，sd = 2））
 
库（ggplot2）
库（RColorBrewer）
库（dplyr）
 
 dat<  -  dat％>％mutate（Y1 = cut（Y，breaks = c -Inf，-3：3，Inf）），
 X1 = cut（X，breaks = c（-Inf，-3：3，Inf）））
 
＃图1 
 ggplot（data = dat，aes（x = Row，y = Col））+ 
 geom _tile（aes（fill = X1），color =black）+ 
 scale_fill_manual（values = c（red，blue，green，purple，pink，yellow， cat1，orange，blue），
 labels = c（cat1，cat2，cat3，cat4，cat5，cat6，cat7，cat8）） 
 
＃图2 
 ggplot（data = dat，aes（x = Row，y = Col））+ 
 geom_tile（aes（fill = Y1），color =black ）+ 
 scale_fill_manual（values = c（red，blue，green，purple，pink，yellow，orange，blue），
标签= c（cat1，cat2，cat3，cat4，cat5，cat6，cat7，cat8） pre 
 
解决方案
您应该可以在 scale_fill_manual 。也就是说，
 
 
  ggplot（data = dat，aes（x = Row，y = Col））+ 
 geom_tile （aes（fill = Y1），color =black）+ 
 scale_fill_manual（values = c（red，blue，green，purple，pink，yellow橙色，蓝色），
标签= c（cat1，cat2，cat3，cat4，cat5，cat6，cat7，cat8），
 drop = FALSE）
  
有关更多信息，请参见？discrete_scale  
 
I am trying to force ggplot to show the legend and fix the colors for a factor even if no value in a range is present.

In the reproducible example below, Figure 1 has at least one value in each range of the variable X1 and plots as desired. Each legend label is plotted and matches the desired color.

In example 2, the variable Y1 does not have a value in each of the ranges that are created. As a result, the plot only shows the first 4 legend labels and uses the first 4 colors.

Is there a way to plot this figure that forces ggplot to show all eight legend labels and fix the colors so that cat1 values are always red, cat2 values are always blue, etc.

I have tried everything I can think of without success.

-- Reproducible example --
set.seed(45678)
dat <- data.frame(Row = rep(x = LETTERS[1:5], times = 10), 
                  Col = rep(x = LETTERS[1:10], each = 5),
                  Y = rnorm(n = 50, mean = 0, sd = 0.5),
                  X = rnorm(n = 50, mean = 0, sd = 2))

library(ggplot2)
library(RColorBrewer)
library(dplyr)

dat <- dat %>% mutate(Y1 = cut(Y, breaks = c(-Inf,-3:3,Inf)),
                      X1 = cut(X, breaks = c(-Inf,-3:3,Inf)))

# Figure 1
ggplot(data =  dat, aes(x = Row, y = Col)) +
  geom_tile(aes(fill = X1), color = "black") +
  scale_fill_manual(values = c("red", "blue", "green", "purple", "pink", "yellow", "orange", "blue"),
                    labels = c("cat1", "cat2", "cat3", "cat4", "cat5", "cat6", "cat7", "cat8"))

# Figure 2
ggplot(data =  dat, aes(x = Row, y = Col)) +
  geom_tile(aes(fill = Y1), color = "black") +
  scale_fill_manual(values = c("red", "blue", "green", "purple", "pink", "yellow", "orange", "blue"),
                    labels = c("cat1", "cat2", "cat3", "cat4", "cat5", "cat6", "cat7", "cat8"))

解决方案
You should be able to use drop = FALSE within scale_fill_manual. That is,
ggplot(data =  dat, aes(x = Row, y = Col)) +
  geom_tile(aes(fill = Y1), color = "black") +
  scale_fill_manual(values = c("red", "blue", "green", "purple", "pink", "yellow", "orange", "blue"),
                    labels = c("cat1", "cat2", "cat3", "cat4", "cat5", "cat6", "cat7", "cat8"), 
                    drop = FALSE)
For more information, see ?discrete_scale

                        
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