Geom_point 和 ggboxplot 以及 ggpair 在 ggplot 中错误地匹配了所有绘图点

Question

我正在尝试一些简单的箱线图，但注意到我在数据框中得到的点只是在 ggplot 中绘制不正确，在所有上述类型的绘图中。

我的数据是

structure(list(rownum = 1:74, Device = c("Dexcom", "Dexcom", 
"Dexcom", "Dexcom", "Dexcom", "Dexcom", "Dexcom", "Dexcom", "Dexcom", 
"Dexcom", "Dexcom", "Dexcom", "Dexcom", "Dexcom", "Dexcom", "Libreview", 
"Libreview", "Libreview", "Libreview", "Libreview", "Libreview", 
"Libreview", "Libreview", "Libreview", "Libreview", "Libreview", 
"Libreview", "Libreview", "Diasend Manual", "Diasend Manual", 
"Diasend Manual", "Diasend Manual", "Diasend Manual", "Diasend Manual", 
"Diasend Manual", "Diasend Manual", "Diasend CGM", "Diasend Manual", 
"Diasend Manual", "Diasend Manual", "Diasend Manual", "Diasend Manual", 
"Diasend CGM", "Diasend CGM", "Diasend Manual", "Diasend Manual", 
"Diasend Manual", "Diasend Manual", "Diasend CGM", "Diasend Manual", 
"Diasend Manual", "Diasend CGM", "Diasend Manual", "Diasend Manual", 
"Diasend Manual", "Diasend Manual", "Diasend Manual", "Diasend CGM", 
"Diasend Manual", "Diasend CGM", "Diasend Manual", "Diasend Manual", 
"Diasend Manual", "Diasend CGM", "Diasend Manual", "Diasend CGM", 
"Diasend Manual", "Diasend Manual", "Diasend Manual", "Diasend Manual", 
"Diasend Manual", "Diasend Manual", "Diasend CGM", "Diasend Manual"
), PREMean = c(10.0484850182022, 7.84715557883709, 7.28766699205132, 
8.47011442894507, 10.7497970736388, 8.6565711351755, 12.2666572965045, 
12.8489327534292, 9.38152123552124, 9.82593283758822, 9.25191807020791, 
10.590004260355, 10.1991015796402, 8.11500023112837, 9.3887371146612, 
9.05289979902383, 16.3938994229184, 11.2269812823576, 8.46589333710567, 
9.45301483336544, 9.654521175124, 9.17169712793734, 5.90663637838715, 
15.1026720647773, 8.73502786461873, 12.515518913676, 10.2021609195402, 
8.88323924469535, 9.138, 10.5977853492334, 14.7827906976744, 
10.9643874643875, 8.04525252525253, 9.2234693877551, 9.2234693877551, 
13.4109826589595, 8.65916169339799, 9.07101449275362, 10.7026923076923, 
17.9097799511002, 6.05655339805825, 7.24913151364764, 7.84826142795985, 
11.6334796926454, 10.0795389048991, 9.63545878693624, 11.7388888888889, 
11.3917218543046, 8.11740335319385, 9.41461318051576, 12.9295681063123, 
10.2035994083164, 7.68975155279503, 10.249885583524, 5.79714285714286, 
10.0638826185102, 8.44704049844237, 10.6952513150205, 9.36492957746479, 
9.83008799318762, 9.6688654353562, 8.00041753653445, 9.26, 9.38389756944444, 
8.55568181818182, 8.63457241816674, 8.12372881355932, 9.84208494208494, 
11.28828125, 9.04013157894737, 11.6740659340659, 9.61797752808989, 
13.8315843798383, 10.1719101123596), POSTMean = c(8.19190208049315, 
7.61158509359437, 7.20120148352596, 8.57923580164976, 10.6268789167925, 
8.37193152150653, 12.3593220150292, 13.9380512091038, 9.30225121492054, 
8.19597861420017, 8.73307014253563, 8.23531795760565, 10.4691064145347, 
8.78835006435006, 9.48096681373489, 9.12521085925145, 13.1253985706432, 
10.2115876974231, 7.65094314018184, 11.1021567021567, 12.3527429320352, 
8.74159058145123, 6.82408707865169, 9.2207729468599, 8.33679846938776, 
11.2045885361817, 12.2492643845594, 8.41001977587343, 8.24191419141914, 
10.7707317073171, 12.2390334572491, 8.28022598870056, 7.67814207650273, 
9.48614130434783, 9.48614130434783, 11.0455128205128, 8.36162310181728, 
10.2825581395349, 10.1807407407407, 16.3283333333333, 7.56851851851852, 
6.80612244897959, 7.6510029661656, 12.1434984833165, 12.2157894736842, 
11.2797101449275, 19.1619047619048, 13.2472361809045, 8.87069342340552, 
8.40763888888889, 13.5286956521739, 10.4632632632633, 8.76877470355731, 
10.6271903323263, 8.2667701863354, 8.61640378548896, 6.96209386281588, 
8.29738799201886, 8.51794871794872, 8.10574666733237, 8.43217993079585, 
7.7244635193133, 13.9224137931034, 9.19426699426699, 8.15335753176044, 
8.30695218383485, 5.89611231101512, 9.45526315789474, 9.406875, 
9.78860759493671, 9.33200934579439, 9.406875, 11.2342145015106, 
11.2984126984127)), row.names = c(NA, -74L), na.action = structure(c(`19` = 19L, 
`30` = 30L, `38` = 38L, `39` = 39L, `42` = 42L, `44` = 44L, `51` = 51L, 
`62` = 62L, `79` = 79L, `84` = 84L), class = "omit"), class = c("tbl_df", 
"tbl", "data.frame"))

然后

ggplot(data, aes(x=PREmean, y=POSTMean)) + geom_point()

绘制一些明显太低的点 - 小于 5。没有一个数字小于 5。

使用 ggboxplot 和 ggpaired 绘图也给我的分数太低了。

我在扯我的头发，我只是不明白为什么这些点显然绘制不正确？请帮忙，谢谢。

Answer 1

正如@RichardTelford 所说，您的情节符合预期。

我已在答案中添加了两个图，以演示 ggplot's 默认轴比例和用户定义比例之间的区别。

ggplot 不知道您将如何解释轴：它只获取每个轴的最小值和最大值，并将它们拟合到可用空间，并在标记刻度线方面做得最好。 ggplot 依赖于读者进行锻炼，在默认版本使用您的data 的情况下，x 轴上的次要网格线表示 2.5，因此 x 原点略大于 5。

如果你想明确坐标轴的值和中断，你必须告诉 ggplot 打印什么。你有很大的灵活性：你可以设置限制、休息和规模......

如果您想要一系列图表的特定限制和中断，那么您最好创建一个为您执行此操作的函数；这是另一个问题的主题；你可以看看这个答案，它将比例从 0 设置为数据的限制：Setting y axis breaks in ggplot

library(ggplot2)
library(patchwork)

p1 <- ggplot(data, aes(x=PREMean, y=POSTMean)) +
  geom_point()+
  ggtitle("Default axis scales")


p2 <- ggplot(data, aes(x=PREMean, y=POSTMean)) +
  geom_point()+
  scale_x_continuous(limits = c(0,20))+
  scale_y_continuous(limits = c(0,20))+
  ggtitle("Defined axis scales")


p1/p2

^{由reprex package (v0.3.0) 于 2020 年 6 月 27 日创建}