Modify legend in facetted plot, ggplot2

Question

For this graph, I want to split the legend into 2 separate legends. One showing the Pulsed Wetlands as circles with the shades corresponding to Wetland number and one showing the Static Wetlands as triangles with the gray shades corresponding to Wetland number. And then the Hydrology legend wouldn't be necessary and I'd like to get rid of that.

Here's what I want the legend to look like (but smaller, of course. This was done in PowerPoint just for demonstration).

I'm pasting the data and the code below.

Data

      Date Hydrology Wetland Temp   Layer
1   15-Jun    Pulsed     One 21.9 Surface
2   15-Jun    Pulsed     One 21.0  Bottom
3    1-Jul    Pulsed     One 28.8 Surface
4    1-Jul    Pulsed     One 23.5  Bottom
5   10-Jul    Pulsed     One 31.8 Surface
6   10-Jul    Pulsed     One 22.6  Bottom
7   14-Jul    Pulsed     One 23.0 Surface
8   14-Jul    Pulsed     One 21.4  Bottom
9   15-Aug    Pulsed     One 28.8 Surface
10  15-Aug    Pulsed     One 28.5  Bottom
11   7-Nov    Pulsed     One 12.1 Surface
12   7-Nov    Pulsed     One  9.9  Bottom
13  15-Jun    Static     Two 22.2 Surface
14  15-Jun    Static     Two 21.2  Bottom
15   1-Jul    Static     Two 29.0 Surface
16   1-Jul    Static     Two 24.1  Bottom
17  10-Jul    Static     Two 30.9 Surface
18  10-Jul    Static     Two 23.3  Bottom
19  14-Jul    Static     Two 25.2 Surface
20  14-Jul    Static     Two 22.6  Bottom
21   1-Aug    Static     Two 27.3 Surface
22   1-Aug    Static     Two 23.5  Bottom
23  15-Aug    Static     Two 26.7 Surface
24  15-Aug    Static     Two 23.6  Bottom
25   7-Nov    Static     Two 11.9 Surface
26   7-Nov    Static     Two  9.0  Bottom
27  15-Jun    Pulsed   Three 21.3 Surface
28  15-Jun    Pulsed   Three 20.9  Bottom
29   1-Jul    Pulsed   Three 26.1 Surface
30   1-Jul    Pulsed   Three 23.8  Bottom
31  10-Jul    Pulsed   Three 30.1 Surface
32  10-Jul    Pulsed   Three 22.8  Bottom
33  14-Jul    Pulsed   Three 23.7 Surface
34  14-Jul    Pulsed   Three 22.2  Bottom
35   7-Nov    Pulsed   Three 12.5 Surface
36   7-Nov    Pulsed   Three 10.0  Bottom
37  15-Jun    Static    Four 21.0 Surface
38  15-Jun    Static    Four 19.3  Bottom
39   1-Jul    Static    Four 25.0 Surface
40   1-Jul    Static    Four 21.2  Bottom
41  10-Jul    Static    Four 25.7 Surface
42  10-Jul    Static    Four 21.3  Bottom
43  14-Jul    Static    Four 22.5 Surface
44  14-Jul    Static    Four 20.8  Bottom
45   1-Aug    Static    Four 24.1 Surface
46   1-Aug    Static    Four 22.8  Bottom
47  15-Aug    Static    Four 25.1 Surface
48  15-Aug    Static    Four 22.2  Bottom
49   7-Nov    Static    Four 12.2 Surface
50   7-Nov    Static    Four  9.1  Bottom
51  15-Jun    Static    Five 19.7 Surface
52  15-Jun    Static    Five 19.2  Bottom
53   1-Jul    Static    Five 24.1 Surface
54   1-Jul    Static    Five 22.9  Bottom
55  10-Jul    Static    Five 24.6 Surface
56  10-Jul    Static    Five 21.7  Bottom
57  14-Jul    Static    Five 21.3 Surface
58  14-Jul    Static    Five 23.0  Bottom
59   1-Aug    Static    Five 23.8 Surface
60   1-Aug    Static    Five 22.0  Bottom
61  15-Aug    Static    Five 24.8 Surface
62  15-Aug    Static    Five 23.1  Bottom
63   7-Nov    Static    Five 11.7 Surface
64   7-Nov    Static    Five  8.8  Bottom
65  15-Jun    Pulsed     Six 21.2 Surface
66  15-Jun    Pulsed     Six 20.4  Bottom
67   1-Jul    Pulsed     Six 24.9 Surface
68   1-Jul    Pulsed     Six 22.5  Bottom
69  10-Jul    Pulsed     Six 28.6 Surface
70  10-Jul    Pulsed     Six 22.0  Bottom
71  14-Jul    Pulsed     Six 21.9 Surface
72  14-Jul    Pulsed     Six 21.4  Bottom
73  15-Aug    Pulsed     Six 27.5 Surface
74  15-Aug    Pulsed     Six 26.1  Bottom
75   7-Nov    Pulsed     Six 13.3 Surface
76   7-Nov    Pulsed     Six  9.5  Bottom
77  15-Jun    Pulsed   Seven 19.7 Surface
78  15-Jun    Pulsed   Seven 18.7  Bottom
79   1-Jul    Pulsed   Seven 23.0 Surface
80   1-Jul    Pulsed   Seven 20.8  Bottom
81  10-Jul    Pulsed   Seven 24.7 Surface
82  10-Jul    Pulsed   Seven 22.2  Bottom
83  14-Jul    Pulsed   Seven 21.3 Surface
84  14-Jul    Pulsed   Seven 20.6  Bottom
85  15-Aug    Pulsed   Seven 26.2 Surface
86  15-Aug    Pulsed   Seven 24.7  Bottom
87   7-Nov    Pulsed   Seven 12.0 Surface
88   7-Nov    Pulsed   Seven 10.5  Bottom
89  15-Jun    Static   Eight 20.6 Surface
90  15-Jun    Static   Eight 19.5  Bottom
91   1-Jul    Static   Eight 28.1 Surface
92   1-Jul    Static   Eight 22.5  Bottom
93  10-Jul    Static   Eight 28.8 Surface
94  10-Jul    Static   Eight 23.1  Bottom
95  14-Jul    Static   Eight 24.7 Surface
96  14-Jul    Static   Eight 21.9  Bottom
97   1-Aug    Static   Eight 25.0 Surface
98   1-Aug    Static   Eight 22.0  Bottom
99  15-Aug    Static   Eight 27.6 Surface
100 15-Aug    Static   Eight 25.3  Bottom
101  7-Nov    Static   Eight 12.1 Surface
102  7-Nov    Static   Eight 10.3  Bottom
103 15-Jun    Static    Nine 20.7 Surface
104 15-Jun    Static    Nine 19.8  Bottom
105  1-Jul    Static    Nine 24.8 Surface
106  1-Jul    Static    Nine 22.7  Bottom
107 10-Jul    Static    Nine 28.3 Surface
108 10-Jul    Static    Nine 22.8  Bottom
109 14-Jul    Static    Nine 23.9 Surface
110 14-Jul    Static    Nine 22.0  Bottom
111  1-Aug    Static    Nine 27.7 Surface
112  1-Aug    Static    Nine 24.5  Bottom
113 15-Aug    Static    Nine 25.8 Surface
114 15-Aug    Static    Nine 23.4  Bottom
115  7-Nov    Static    Nine 11.9 Surface
116  7-Nov    Static    Nine  9.5  Bottom
117 15-Jun    Pulsed     Ten 22.3 Surface
118 15-Jun    Pulsed     Ten 21.9  Bottom
119  1-Jul    Pulsed     Ten 29.6 Surface
120  1-Jul    Pulsed     Ten 28.2  Bottom
121 10-Jul    Pulsed     Ten 33.0 Surface
122 10-Jul    Pulsed     Ten 30.4  Bottom
123 14-Jul    Pulsed     Ten 25.6 Surface
124 14-Jul    Pulsed     Ten 24.1  Bottom
125  7-Nov    Pulsed     Ten 13.2 Surface
126  7-Nov    Pulsed     Ten 10.1  Bottom 

Code

colvec <-c("white", "white","gray80", "gray80", "gray60", "gray60", "gray37", "gray37","black", "black")  
water$Layer=factor(water$Layer, c("Surface", "Bottom"))
water$Date=factor(water$Date, c("15-Jun", "1-Jul", "10-Jul", "14-Jul", "1-Aug", "15-Aug", "7-Nov"))
water$Wetland=factor(water$Wetland, c("One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten"))

ggplot(water, aes(Date, Temp, group=Wetland, shape=Hydrology)) +
  geom_point(size =4, color = "black")+
  geom_point(aes(color=Wetland),size=3) +
  scale_colour_manual(values=colvec) +
  facet_grid(Layer ~ Hydrology) 

Thanks,

-Sarah

Answer 1

Here is a solution inspired by this question

First, made new variable colvec2 that contains all colors only once.

colvec2 <-c("white", "gray80", "gray60", "gray37",  "black")  
colvec <-c("white", "white","gray80", "gray80", "gray60", "gray60", "gray37", "gray37","black", "black")  

Original plot saved as object and without the legend.

p<-ggplot(water, aes(Date, Temp, group=Wetland, shape=Hydrology)) +
  geom_point(aes(color=Wetland),size=3) +
  scale_colour_manual(values=colvec) +
  facet_grid(Layer ~ Hydrology) +
  theme(legend.position="none")

Plot that contains only data of Pulsed. Set shape=16 inside the geom_point(). With scale_colour_manual() changed legend title and colors.

p1<-ggplot(subset(water,Hydrology=="Pulsed"), 
     aes(Date, Temp, group=Wetland, shape=Hydrology)) +
  geom_point(aes(color=Wetland),size=3,shape=16) +
  scale_colour_manual("Pulsed Wetlands",values=colvec2) +
  facet_grid(Layer ~ Hydrology)

The same as p1, only for Static.

p2<-ggplot(subset(water,Hydrology=="Static"), 
      aes(Date, Temp, group=Wetland, shape=Hydrology)) +
  geom_point(aes(color=Wetland),size=3,shape=17) +
  scale_colour_manual("Static Wetlands",values=colvec2) +
  facet_grid(Layer ~ Hydrology)

Save plots p1 and p2 using ggplot_build() and ggplot_gtable().

pt1<-ggplot_gtable(ggplot_build(p1))
pt2<-ggplot_gtable(ggplot_build(p2))

Extract just grob of legends for both plots. This time legends are in 12. element (element containing guide-box)

leg1<-pt1$grobs[[12]]
leg2<-pt2$grobs[[12]]

Now use grid.arrange() and arrangeGrob() to plot all parts.

library(gridExtra)
grid.arrange(arrangeGrob(p,arrangeGrob(leg1,leg2), ncol = 2,widths=c(3/4,1/4)))