Side by Side plot with one legend in ggplot2

Question

I would like to know how to use ggplot2 to create a side by side plots with one common legend. I have seen some similar questions but not sure how to directly apply it to my code. I have provided my code for the graphs with the legend and some data that can be used to recreate the graphs.

Stocks1<-c(2,1,0.8,0.7,0.6)
Bonds1<-c(1,0.8,0.7,0.6,0.5)
Cash1<-1-(Stocks1+Bonds1)
Stocks2<-c(0.6,0.5,0.4,0.3,0.2)
Bonds2<-c(0.3,0.2,0.2,0.15,0.1)
Cash2<-1-(Stocks2+Bonds2)
H<-length(Stocks1) #Change value to represent data
t <- seq(from = 0, to = H, 1) # time grid

And here are the two graphs

pi_F<- data.frame(cash = Cash1,  bonds = Bonds1,   
                  stocks= Stocks1,time=t[-1])
melted_F   <- melt(pi_F, id.vars = 'time')

ggplot(melted_F, aes(x=time, y=value, group = variable)) +
  geom_area(aes(fill=variable)) +
  scale_fill_manual(values=c("#2E318F", "#DFAE41","#109FC6"),
                    name="Asset Type",
                    labels = c("Bank account","Bonds", "Stocks"))+
  scale_x_continuous(name = 'Age',
                     breaks = seq(1,H,1)) + 
  scale_y_continuous(name = 'Asset allocation (in %)',
                     labels=scales::percent,
                     breaks = seq(0,1,0.1),
                     sec.axis = sec_axis(~.*1,breaks =  seq(0,1,0.1),labels=scales::percent)) + 
  coord_cartesian(xlim = c(1,H), ylim = c(0,1), expand = TRUE) +
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank())

pi_F<- data.frame(cash = Cash2,  bonds = Bonds2,   
                  stocks= Stocks2,time=t[-1])
melted_F   <- melt(pi_F, id.vars = 'time')

ggplot(melted_F, aes(x=time, y=value, group = variable)) +
  geom_area(aes(fill=variable)) +
  scale_fill_manual(values=c("#2E318F", "#DFAE41","#109FC6"),
                    name="Asset Type",
                    labels = c("Bank account","Bonds", "Stocks"))+
  scale_x_continuous(name = 'Age',
                     breaks = seq(1,H,1)) + 
  scale_y_continuous(name = 'Asset allocation (in %)',
                     labels=scales::percent,
                     breaks = seq(0,1,0.1),
                     sec.axis = sec_axis(~.*1,breaks =  seq(0,1,0.1),labels=scales::percent)) + 
  coord_cartesian(xlim = c(1,H), ylim = c(0,1), expand = TRUE) +
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank())

Idealy I would like these side by side with the legend in an appropriate place, probably to the right of both graphs. Thanks in advance for the help!

Don't give different data frames the same name - that is confusing. — Gregor Thomas, Oct 23 '20 at 14:19
I find that the simplest way to do this is to use the package `patchwork`, created by the person that now maintains `ggplot2`. Having named the two plots (e.g. `g1` and `g2`), you then call: `g1 + g2 + plot_layout(guides = 'collect')` — p0bs, Oct 23 '20 at 14:44

score 4 · Accepted Answer · answered Oct 23 '20 at 14:25

Put your data together and use facets:

## calling the first data `melted_F` and the second `melted_F2`
## put them in one data frame with a column named "data" to tell
## which is which
melted = dplyr::bind_rows(list(data1 = melted_F, data2 = melted_F2), .id = "data")

## exact same plot code until the last line
ggplot(melted, aes(x=time, y=value, group = variable)) +
  geom_area(aes(fill=variable)) +
  scale_fill_manual(values=c("#2E318F", "#DFAE41","#109FC6"),
                    name="Asset Type",
                    labels = c("Bank account","Bonds", "Stocks"))+
  scale_x_continuous(name = 'Age',
                     breaks = seq(1,H,1)) + 
  scale_y_continuous(name = 'Asset allocation (in %)',
                     labels=scales::percent,
                     breaks = seq(0,1,0.1),
                     sec.axis = sec_axis(~.*1,breaks =  seq(0,1,0.1),labels=scales::percent)) + 
  coord_cartesian(xlim = c(1,H), ylim = c(0,1), expand = TRUE) +
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank()) +
  ##  facet by the column that identifies the data source
  facet_wrap(~ data)

Wow......thank you so much for your quick and helpful response. I really appreciate it! Saved me a real head ache :) :) — Shem Katz, Oct 23 '20 at 14:39

Side by Side plot with one legend in ggplot2

1 Answers1