ggplot - 直方图 - 按组划分的密度图：只出现一组

Question

我有一个小数据集，我想使用 ggplot 按组绘制 histogram/density 图。我的数据集如下：

> data_Test_augm
     mpg cyl4 cyl6 cyl8  disp  hp drat    wt  qsec vs0 vs1 gear3 gear4 gear5 carb1 carb2 carb3 carb4 carb6 carb8 am  predictions
 1: 21.0    0    1    0 160.0 110 3.90 2.620 16.46   1   0     0     1     0     0     0     0     1     0     0  1 1.000000e+00
 2: 21.4    0    1    0 258.0 110 3.08 3.215 19.44   0   1     1     0     0     1     0     0     0     0     0  0 7.884922e-12
 3: 17.8    0    1    0 167.6 123 3.92 3.440 18.90   0   1     0     1     0     0     0     0     1     0     0  0 7.884924e-12
 4: 32.4    1    0    0  78.7  66 4.08 2.200 19.47   0   1     0     1     0     1     0     0     0     0     0  1 1.000000e+00
 5: 30.4    1    0    0  75.7  52 4.93 1.615 18.52   0   1     0     1     0     0     1     0     0     0     0  1 7.884886e-12
 6: 19.2    0    0    1 400.0 175 3.08 3.845 17.05   1   0     1     0     0     0     1     0     0     0     0  0 7.884923e-12
 7: 26.0    1    0    0 120.3  91 4.43 2.140 16.70   1   0     0     0     1     0     1     0     0     0     0  1 1.000000e+00
 8: 30.4    1    0    0  95.1 113 3.77 1.513 16.90   0   1     0     0     1     0     1     0     0     0     0  1 7.884916e-12
 9: 19.7    0    1    0 145.0 175 3.62 2.770 15.50   1   0     0     0     1     0     0     0     0     1     0  1 1.000000e+00
10: 21.4    1    0    0 121.0 109 4.11 2.780 18.60   0   1     0     1     0     0     1     0     0     0     0  1 7.884918e-12

我的代码如下：

data_Test_augm$am <- factor(data_Test_augm$am, levels = c("1" , "0"))  #Sets the faactor levels in the desired order

ggplot(data_Test_augm, aes(x = predictions, fill = am , color = am )) +
  geom_histogram(aes(y=..density..), position="identity",alpha = 0.4) + guides(color = FALSE) +
  geom_density (alpha = 0.5)+ 
  labs(title = "Predicted Probabilities per am in the Test Dataset", 
       x = "Predicted Probability of being in am 1", y = "Count") + 
  scale_fill_manual(limits=c('1', '0'),              # Defines the mapping between factor levels, labels and colors
                    labels = c("Positive", "Negative"), 
                    values = c("red", 'blue')) + 
  labs(fill="am")+  # Sets the title of the legend
  guides(color=FALSE)  # Hides the legend for Color

这是输出：

我不明白为什么分组变量 am 中只有一个水平出现在图中。

Answer 1

我觉得更像是一个评论，但是因为我的声望太低而写不出来

你确定要密度吗？没有它你会得到一个很好的直方图：

dt <- data.frame(am = c(1,0,0,1,1,0,1,1,1,1), 
predictions = c(1,7.884922e-12,7.884924e-12,1,7.884886e-12,7.884923e-12,1,7.884916e-12,1,7.884918e-12))
dt$am <- factor(dt$am, levels = c("1" , "0"))

g <- ggplot(dt, aes(x = predictions, fill = am))
g+geom_histogram(aes(y=..density..), position="identity",alpha = 0.4) + 
labs(title = "Predicted Probabilities per am in the Test Dataset",
x = "Predicted Probability of being in am 1", y = "Count") +
scale_fill_manual(limits=c('1', '0'),              
labels = c("Positive", "Negative"),
values = c("red", 'blue')) +
labs(fill="am")

我刚删除了geom_density（还有颜色映射，你已经有填充了！）。这就是我得到的： Histogram

密度问题可能是因为数据很奇怪。对于 am = 0，您有 100% 的概率进入 7.88492e-12 和 7.88493e-12 之间的区间。虽然它甚至不使用你的颜色...

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