ggplot：无变量名在scale_continuous和coord_cartesian中访问aes的x/y

在管道中调用ggplot2绘图时，无需指定实际变量名的场景下，scale_x_continuous()可通过公式正常访问x变量，但scale_y_continuous()调用y变量时报错；coord_cartesian()中访问x或y变量均报错，且错误信息不同。绘图逻辑已嵌入大型函数与循环，需尽量精简脚本，避免新增额外函数。

可行代码 #

df%>%
{ggplot(., aes(x=var1, y=var2, group=var1)) + 
  geom_boxplot() +
  scale_x_continuous(limits=~c(min(.x), max(.x)+2))
} 

失败代码：scale_y_continuous调用y变量 #

df%>%
{ggplot(., aes(x=var1, y=var2, group=var1)) + 
  geom_boxplot() +
  scale_y_continuous(limits=~c(min(.y), max(.y)))
} 

报错信息：

Error in limits(...) : the ... list contains fewer than 2 elements

失败代码：coord_cartesian调用x变量 #

df%>%
{ggplot(., aes(x=var1, y=var2, group=var1)) + 
  geom_boxplot() +
  coord_cartesian(xlim=~c(min(.x), max(.x)+2))
} 

报错信息：

Error in rep(no, length.out = len) :
attempt to replicate an object of type 'language'
In addition: Warning message:
In is.na(coord_limits) :
is.na() applied to non-(list or vector) of type 'language'

示例数据 #

structure(list(var2 = c(41.8158776557993, 370.010906325126, 29.9762384196746, 
134.592293143879, 25.4992538620678, 287.238664871234, 65.7100626815271, 
634.948823559833, 91.5948027086723, 86.7615693041168, 44.5224518361713, 
102.862000210952, 76.9514655241161, 149.313762170598, 109.483295036156, 
74.7833526120967, 80.3239106567395, 55.9682231819449, 26.7674658360997, 
105.660918410594, 224.370801592227, 30.6596504549054, 102.702090128488, 
70.4815806356089, 53.1717647655692, 65.3593580730541, 54.2854779330253, 
102.059837709769, 47.2096844771118, 77.1587206126892, 33.0648643220668, 
276.926923446508, 102.746050916705, 107.401093976279, 167.818090038351, 
71.8878648913058, 668.341966934719, 69.1955286005593, 224.429169496685, 
105.176801504246, 36.5636545543272, 27.3579424588226, 99.1295846081317, 
22.6118540567448, 62.8144181201643, 338.817547088697, 46.6838495612109, 
36.3049947573018, 233.886743305712, 63.5068060066697, 27.362029620246, 
207.076466663575, 10.8638328031731, 33.0598772890319, 156.356357882702, 
102.796465580563, 51.0078571075201, 592.423239489015, 25.395651904048, 
10.6840046287661, 86.2638933290398, 9.37293513355443, 12.1045509288724, 
31.6762598831153, 15.8311155913569, 114.1535840353, 39.8158400480808, 
5.86158006646743, 23.4571077463048, 45.4030757053628, 22.2904441671737, 
12.4718430344437, 8.58691755607576, 21.7628902890272, 18.1667283040004, 
19.6287558593084, 23.5832776183889, 26.9071136091838, 34.7483836224121, 
20.2304056642373, 57.8445206474536, 36.0921278909265, 24.6660469176245, 
45.0881208322003, 13.0269962638014, 52.8209485245866, 36.1048602221464, 
12.3145978252099, 27.51555570049, 29.5034414222287, 362.342060143168, 
181.025704198042, 29.0834989975671, 7.38318949359624, 9.68216908583276, 
78.1173130093021, 12.3355705438994, 15.1914457964689, 144.910200824294, 
76.921000102776, 25.3898343301642, 14.5850919046431, 50.3066458452342, 
249.205645506716, 205.560323463066, 25.3736066368173, 7.81881404460238, 
19.4358320599181, 13.1654712241464, 24.005085534781, 249.549219626201, 
7.88251811063204, 15.7572592299871, 24.7402432626252, 17.8322442392071, 
47.0019810880816, 28.0830030911662, 18.2807759776457, 16.5785887094536, 
8.34646734403808, 22.3722609837999, 160.557334051436, 54.2469201496058, 
46.0961067666223, 24.9813791029581, 75.0513867662843, 308.591282693212, 
14.1925725276128, 42.8733361079367, 16.5666721486842, 16.0430116319228, 
13.5016194981692, 15.628997969955, 9.82971641591987, 8.23243352931862, 
13.1310500626603, 21.8406849708019, 15.9875238399488, 26.9243510470804, 
23.9134978932328, 9.62005498155129, 22.1471632244552, 13.6769758141992, 
28.2252127082182, 298.650310547727, 61.0877737345033, 26.8300363380246, 
8.32592072637992, 7.27900393186264, 19.103406780395), var1 = c(1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L)), class = "data.frame", row.names = c(NA, 
-150L))

问题原因与解决方案 #

1. scale_y_continuous报错解决 #

scale_x_continuous()的limits参数默认将x变量传入公式作为.x，但scale_y_continuous()无此默认映射，需直接从管道数据中提取y变量：

df%>%
{ggplot(., aes(x=var1, y=var2, group=var1)) + 
  geom_boxplot() +
  scale_y_continuous(limits=~c(min(.$var2), max(.$var2)))
} 

或用with()简化：

df%>%
{with(., ggplot(., aes(x=var1, y=var2, group=var1)) + 
  geom_boxplot() +
  scale_y_continuous(limits=c(min(var2), max(var2)))
)}

2. coord_cartesian报错解决 #

coord_cartesian()的xlim/ylim不支持公式接口，必须传入具体数值，直接从管道数据计算即可：

df%>%
{ggplot(., aes(x=var1, y=var2, group=var1)) + 
  geom_boxplot() +
  coord_cartesian(xlim=c(min(.$var1), max(.$var1)+2))
} 

3. 通用精简写法（适配循环与函数） #

若需重复使用轴限，可在管道内提前计算，避免重复提取：

df%>%
{
  x_lim <- c(min(.$var1), max(.$var