Nu  Cd_ppm  pH
1   0.024   5.51
2   0.023   5.53
3   0.024   5.60
4   0.025   5.60
5   0.025   6.41
6   0.024   6.38
7   0.024   6.42
8   0.026   6.39
9   0.016   6.45
10  0.015   6.46
11  0.016   6.46
12  0.014   6.44
13  0.018   7.00
14  0.017   7.10
15  0.017   7.05
16  0.023   7.01
17  0.030   6.80
18  0.034   6.88
19  0.030   6.87
20  0.035   6.89
21  0.024   6.21
22  0.029   6.18
23  0.028   6.21
24  0.031   6.21
25  0.019   6.43
26  0.023   6.38
27  0.021   6.41
28  0.029   6.39
29  0.027   6.98
30  0.025   6.91
31  0.026   6.71
32  0.029   6.67
33  0.037   6.45
34  0.039   6.41
35  0.038   6.48
36  0.037   6.48
37  0.047   6.42
38  0.043   6.36
39  0.051   6.36
40  0.048   6.40
41  0.033   5.95
42  0.036   6.02
43  0.038   5.96
44  0.038   5.95
45  0.041   6.13
46  0.042   6.14
47  0.040   6.13
48  0.048   6.15
49  NA  NA
50  0.006   6.02
51  0.007   6.06
52  0.007   5.99
53  0.080   5.93
54  0.088   5.89
55  0.079   5.86
56  0.079   5.80
57  0.053   7.84
58  0.051   7.87
59  0.069   7.93
60  0.052   7.95
61  0.046   6.04
62  0.048   5.98
63  0.038   6.28
64  0.045   6.54
65  0.176   6.59
66  0.172   6.14
67  0.176   6.38
68  0.176   6.60
69  0.113   6.10
70  0.116   6.14
71  0.114   6.13
72  0.111   6.11
73  0.095   7.06
74  0.065   7.05
75  0.084   7.03
76  0.063   7.01
77  0.048   7.18
78  0.053   7.16
79  0.052   7.28
80  0.051   7.11
81  0.045   7.61
82  0.038   7.62
83  0.046   7.59
84  0.046   7.60
85  0.025   7.51
86  0.026   7.53
87  0.029   7.49
88  0.030   7.54
89  0.030   6.82
90  0.030   6.78
91  0.031   6.82
92  0.031   6.80
93  0.075   6.95
94  0.079   6.90
95  0.076   6.95
96  0.079   6.93
97  0.059   7.39
98  0.065   7.37
99  0.059   7.42
100 0.061   7.41
101 0.038   7.08
102 0.042   7.14
103 0.049   7.24
104 0.058   7.12
105 0.063   7.11
106 0.068   7.11
107 0.058   7.03
108 0.059   7.13
109 0.072   6.67
110 0.076   6.56
111 0.071   6.66
112 0.072   6.59
113 0.113   6.86
114 0.123   6.87
115 0.117   6.81
116 0.114   6.91
117 0.093   6.71
118 0.091   6.71
119 0.090   6.75
120 0.090   6.70
121 0.087   6.63
122 0.099   6.49
123 0.098   6.52
124 0.099   6.45
125 0.010   8.07
126 0.009   8.01
127 0.010   8.06
128 0.009   8.06

my.formula= y ~ exp(1.5*-x)
Pot=data[c(1:52),]
Pot1=data[c(53:64),]
Incub=data[c(65:76),]
Incub1=data[c(77:128),]

library(gridExtra)
library(tidyverse)
library(reshape2)
library(dplyr)
library(reshape2)
library(tidyr)
library(ggpmisc)
library(ggpubr)
library(patchwork) # combine plots
library(gapminder)

p1=ggplot(data=data, aes(x=pH,y=Cd_ppm,col="+Pl (l, control)", col="-Pl (l, control)"))+
  
  geom_point( size=3.5, data = Pot, shape=16)+labs(x="pH", y=expression(Cd~~~mg~(kg~soil)^{-1}))+
  geom_point(size=3.5, data=Pot1,  shape=17)+
  geom_point(size=3.5, data=Incub,  shape=2)+
  geom_point(size=3.5, data=Incub1,  shape=1)+
  geom_smooth(data = subset(data, Nu<53),formula= y ~ exp(1.5*-x), method = "lm", se=F, level=0.95, size=0.5,aes(col="+Pl ( Compost, FS, Fe)"))+
  geom_smooth(data = subset(data, Nu %in% c(53:64)),formula= y ~ exp(1.5*-x), method = "lm", se=F, level=0.95,size=0.5,linetype="dashed", col="black")+
  geom_smooth(data = subset(data, Nu %in% c(65:76)),formula= y ~ exp(1.5*-x), method = "lm", se=F, level=0.95,size=0.5,linetype="dashed", col="black")+
  geom_smooth(data = subset(data, Nu>76),formula= y ~ exp(1.5*-x), method = "lm", se=F, level=0.95, size=0.5,aes(col="-Pl ( Compost, FS, Fe)"))+
  stat_poly_eq(data = subset(data, Nu<53),formula= y ~ exp(1.5*-x),aes(label=paste(..rr.label..)),  
               label.x.npc = "left", label.y.npc = 0.03,  parse=T, size=6, col="black")+
  stat_poly_eq(data = subset(data, Nu=53:64),formula= y ~ exp(1.5*-x),aes(label=paste(..rr.label..)),  
               label.x.npc = "left", label.y.npc = 0.1,  parse=T, size=6, col="black")+
  
  stat_poly_eq(data = subset(data, Nu>76),formula= y ~ exp(1.5*-x),aes(label=paste( ..rr.label..)), 
               label.x.npc = "right", label.y.npc = 0.8, parse=T, size=6, col="black", vjust=2, show.legend=F)+
  stat_poly_eq(data = subset(data, Nu=65:76),formula= y ~ exp(1.5*-x),aes(label=paste(..rr.label..)), 
               label.x.npc = "right", label.y.npc = 0.9, parse=T, size=6, col="black", vjust=2, show.legend=F)+
   theme(legend.text = element_text(colour="black", size=17,face=1))+
  theme(legend.position = "bottom") +
  guides(color = guide_legend(nrow = 2, byrow = T))+
  scale_colour_manual(labels=c(col="Pot liming", col="Incubation liming", col="Incubation", col="Pot"),values = c("black", "black", "black", "black"))+
  guides(col = guide_legend(override.aes = list(linetype=c(0,0), shape = c(1, 2, 16, 17), color="black")))

png(file="grafic1.png",height = 125, width = 150, unit ="mm", res = 300)
(mfrow=c(2,2))
ggarrange(p1,  ncol=1, nrow=1, common.legend = T, legend="bottom")
dev.off()

您好，我正在尝试将图中的图例拆分为两行。但它不起作用。如果有人给我写一个解决方案，我将非常感谢任何建议。图中的图例由一行组成，我想将其拆分为两行。