用R语言ggplot2拼接多个分组曲线图时某条折线出现偏移

Question

用R语言ggplot2拼接多个分组曲线图时某条折线出现偏移

两个分组曲线图分开绘制都正常，但是两个图合并到一起，用cowplot做成一页多图形式就会出现其中一条折线的位置发生向上偏移

分开绘制结果如下：

一页多图结果如下

代码如下：

library(ggplot2)
library(cowplot)

x = c(1,2,3,4)
b1 = c(0.0457,0.038,0.0304,0.0139)
b2 = c(0.0704,0.0642,0.0574,0.044)
b3 = c(0.1284,0.1244,0.1152,0.1036)
b4 = c(0.1255,0.1186,0.1034,0.0941)
b5 = c(0.1346,0.1247,0.118,0.1059)
m = c(0.1373,0.1351,0.137,0.1399)
m1 = c(0.1324,0.1286,0.1324,0.1282)
m2 = c(0.055,0.0537,0.0596,0.0609)
m3 = c(0.1134,0.1118,0.1167,0.1181)

p1 <- ggplot()+
  theme_bw()+
  geom_line(aes(x, m, color="1"))+
  geom_point(aes(x, m, color="1"),size=1)+
  geom_line(aes(x, b1, color="2"))+
  geom_point(aes(x, b1, color="2"),size=1)+
  geom_line(aes(x, b2, color="3"))+
  geom_point(aes(x, b2, color="3"),size=1)+
  geom_line(aes(x, b3, color="4"))+
  geom_point(aes(x, b3, color="4"),size=1)+
  geom_line(aes(x, b4, color="5"))+
  geom_point(aes(x, b4, color="5"),size=1)+
  geom_line(aes(x, b5, color="6"))+
  geom_point(aes(x, b5, color="6"),size=1)+
  geom_line(aes(x, m1, color="7"))+
  geom_point(aes(x, m1, color="7"),size=1)+
  geom_line(aes(x, m2, color="8"))+
  geom_point(aes(x, m2, color="8"),size=1)+
  geom_line(aes(x, m3, color="9"))+
  geom_point(aes(x, m3, color="9"),size=1)+
  xlab("(1)")+
  ylab("y")+
  scale_y_continuous(limits = c(0,0.16),breaks=seq(0,0.16,0.02))+
  labs(colour = "group")+
  theme(text=element_text("serif"))+
  theme(text = element_text(size=7),
        legend.key.height = unit(0.2,"cm"))

#print(p1)

m2 <- c(0.1468,0.1423,0.1508,0.1501)
b12 <- c(0.0497,0.0436,0.0342,0.0165)
b22 <- c(0.0727,0.0636,0.0547,0.0462)
b32 <- c(0.1362,0.1284,0.1217,0.1049)
b42 <- c(0.1307,0.1224,0.1106,0.0907)
b52 <- c(0.1486,0.1392,0.1334,0.1196)
m12 <- c(0.1314,0.1308,0.1376,0.1298)
m22 <- c(0.0569,0.0544,0.0614,0.0601)
m32 <- c(0.1195,0.117,0.1237,0.1258)

p2 <- ggplot()+
  theme_bw()+
  geom_line(aes(x, m2, color="1"))+
  geom_point(aes(x, m2, color="1"),size=1)+
  geom_line(aes(x, b12, color="2"))+
  geom_point(aes(x, b12, color="2"),size=1)+
  geom_line(aes(x, b22, color="3"))+
  geom_point(aes(x, b22, color="3"),size=1)+
  geom_line(aes(x, b32, color="4"))+
  geom_point(aes(x, b32, color="4"),size=1)+
  geom_line(aes(x, b42, color="5"))+
  geom_point(aes(x, b42, color="5"),size=1)+
  geom_line(aes(x, b52, color="6"))+
  geom_point(aes(x, b52, color="6"),size=1)+
  geom_line(aes(x, m12, color="7"))+
  geom_point(aes(x, m12, color="7"),size=1)+
  geom_line(aes(x, m22, color="8"))+
  geom_point(aes(x, m22, color="8"),size=1)+
  geom_line(aes(x, m32, color="9"))+
  geom_point(aes(x, m32, color="9"),size=1)+
  xlab("(2)")+
  ylab("y")+
  scale_y_continuous(limits = c(0,0.16),breaks=seq(0,0.16,0.02))+
  labs(colour = "group")+
  theme(text=element_text("serif"))+
  theme(text = element_text(size=7),
        legend.key.height = unit(0.2,"cm"))

#print(p2)
p <- cowplot::plot_grid(p1, p2, nrow = 1)
print(p)

其中分开绘制的图（1）（2）都是正常的，但是利用cowplot一页多图将两张图拼接到一起，就会出现图（1）的紫色折线发生偏移，请问各位这是什么原因导致的，怎样解决？

Answer 1

如果将多个分组图拼接在一起时 ggplot2 图中的折线发生偏移，则可能是由于两个图之间的比例差异所致。 要解决此问题，您可以尝试匹配两个图的比例。 例如，您可以对两个图形使用相同的比例限制或使用 ggplot2 中的 coord_cartesian() 函数为两个图形设置相同的坐标系。

以下是如何为两个图形设置相同坐标系的示例：

library(ggplot2)

# First graph
g1 <- ggplot(mtcars, aes(wt, mpg)) +
  geom_point() +
  coord_cartesian(xlim = c(2, 5), ylim = c(10, 35))

# Second graph
g2 <- ggplot(mtcars, aes(wt, drat)) +
  geom_point() +
  coord_cartesian(xlim = c(2, 5), ylim = c(2, 5))

# Combine the two graphs
library(cowplot)
plot_grid(g1, g2, ncol = 2)

这样，两个图形将具有相同的比例限制，折线不应再偏移。