June 2020
Beginner to intermediate
522 pages
9h 6m
Chinese
Content preview from R 语言经典实例（原书第 2 版）
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图形
｜
295
许多点都很接近直线，特别是中间部分的点，但尾部的点偏离直线相当远。Q-Q 线上方
的点太多，表示大体向左偏的趋势。
向左偏斜可以通过对数变换来进行纠正。我们可以绘制 log(Price)，得到图 10-50：
ggplot(Cars93, aes(sample = log(Price))) +
stat_qq() +
stat_qq_line()
sample
4.0
3.5
3.0
2.5
2.0
1.5
0
theoretical
-
2
-
1 1 2
图 10-50：汽车价格对数变换后的 Q-Q 图
注意，新图中点的表现要好得多，除了最左边的尾部外，大部分点与对角线直线保持很
近距离。似乎 log(Price) 是近似正态的。
10.21.4 另请参阅
有关为其他分布创建 Q-Q 图的信息，请参见 10.22 节。有关应用正态 Q-Q 图诊断线性回
归的内容，请参阅 11.16 节。
10.22 创建其他 Q-Q 图
10.22.1 问题
需要查看非正态分布数据的 Q-Q 图。
10.22.2 解决方案
对于这个方法，你必须先具备有关分布的一些知识。该解决方案由以下步骤构成：
296
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第
10
章
1. 使用 ppoints 函数生成 0 到 1 之间的点序列。
2. 使用分位数函数将这些点转换为分位数。
3. 对样本数据进行排序。 ...
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