ggplot2: Creating a legend which includes multiple symbols, line types, and colors

Question

I'm trying create a function that will plot measured stream values (as unconnected points), as well as a smooth curve of modeled values. I'd like to be able to make a unique shape for each type of streamflow (15-min vs 24-hour), and also have a unique color and line type for the two model flows.

I have been able to create different colors for my measured values and have that show up correctly in the legend, but when I try to alter the shapes, I get into trouble. Same for trying to match up dashed and solid lines in my curves. I'd tried changing geom_point() + to geom_point(shape = variable) + but that produces this error: Error in layer(data = data, mapping = mapping, stat = stat, geom = GeomLine, : object 'variable' not found

ggplot(data = r1,aes(x=ReturnPeriod, y=value, color=variable)) +
  geom_point()+
  geom_line(data = r2,aes(x=ReturnPeriod, y=value))+
  ylab("Max Yearly Flow (cfs)") +
  xlab("Return Interval (years)") +
  scale_shape_manual(name = "Legend", 
                      labels = c("Obs 15-min", "Obs 24-hour", "15-min P3", "24-hr P3"),
                      values = c("Peak_cfs"=16, "Daily_cfs"=17, "PeakEst"=NA, 
                                 "DailyEst" = NA)) +
  scale_colour_manual(name = "Legend", 
                      labels = c("Obs 15-min", "Obs 24-hour", "15-min P3", "24-hr P3"),
                      values = c("Peak_cfs"="grey", "Daily_cfs"="black", "PeakEst"="dark grey", 
                                 "DailyEst" = "black")) +
  scale_linetype_manual(name = "Legend", 
                        labels = c("Obs 15-min", "Obs 24-hour", "15-min P3", "24-hr P3"),
                        values = c("Peak_cfs"="blank", "Daily_cfs"="blank", "PeakEst"="solid", 
                                   "DailyEst" = "dashed"))+
  guides(colour = guide_legend(override.aes = list(
    linetype = c("blank", "blank", "solid", "dashed"),
    shape = c(16,17,NA,NA),
    color = c("grey","black", "dark grey", "black")))) +
  theme(legend.position=c(0.92, 0.2),  
        legend.background = element_rect(fill="white"),
        legend.key = element_blank(),
        legend.box = "horizontal")

My data is:

r1 = read.table(
  header = TRUE,
  stringsAsFactors = FALSE,
  text = 
"ReturnPeriod  variable value
1      1.090909 Daily_cfs  14.3
2      1.200000 Daily_cfs  52.3
3      1.333333 Daily_cfs  66.6
4      1.500000 Daily_cfs  93.3
5      1.714286 Daily_cfs  94.3
6      2.000000 Daily_cfs 103.0
7      2.400000 Daily_cfs 107.0
8      3.000000 Daily_cfs 119.0
9      4.000000 Daily_cfs 123.0
10     6.000000 Daily_cfs 166.0
11    12.000000 Daily_cfs 207.0
12     1.090909  Peak_cfs  29.0
13     1.200000  Peak_cfs 159.0
14     1.333333  Peak_cfs 241.0
15     1.500000  Peak_cfs 255.0
16     1.714286  Peak_cfs 296.0
17     2.000000  Peak_cfs 320.0
18     2.400000  Peak_cfs 339.0
19     3.000000  Peak_cfs 351.0
20     4.000000  Peak_cfs 512.0
21     6.000000  Peak_cfs 737.0
22    12.000000  Peak_cfs 800.0"
)

r2 <- read.table(
  header = TRUE,
  stringsAsFactors = FALSE,
  text = 
    "ReturnPeriod variable      value
1      1.010101 DailyEst   8.185016
2      2.000000 DailyEst 104.434396
3      4.000000 DailyEst 148.084828
4     10.000000 DailyEst 180.992656
5     25.000000 DailyEst 199.429333
6     50.000000 DailyEst 207.967918
7      1.010101  PeakEst  14.846387
8      2.000000  PeakEst 349.352462
9      4.000000  PeakEst 547.379809
10    10.000000  PeakEst 713.827969
11    25.000000  PeakEst 815.243158
12    50.000000  PeakEst 865.063562"
)

I'm expecting to get triangle symbols for the Obs 24-hour in the graph, instead I'm getting circles, and in both the legend and graph, I'm trying to get the solid black line to be a dashed black line.

Graph produced by current code:

If you want the linetype to connect to something in the data, you need to specify that inside aes(). Presumably (in your geom_line layer) aes(linetype = variable) — Gregor Thomas

Reese Withouterspoon Reese Withouterspoon · Accepted Answer · 2019-05-01T05:57:32

If you combine r1 and r2 into r3 for plotting and add shape + linetype to aes , it will work

library(ggplot2)

r1$variable <- factor(r1$variable)
r2$variable <- factor(r2$variable)
r3 <- rbind(r1, r2)

ggplot(data = r3, aes(x=ReturnPeriod, y=value, color=variable, shape=variable)) +
  geom_point()+
  geom_line(aes(linetype=variable))+
  ylab("Max Yearly Flow (cfs)") +
  xlab("Return Interval (years)") +
  scale_shape_manual(name = "Legend", 
                     labels = c("Obs 15-min", "Obs 24-hour", "15-min P3", "24-hr P3"),
                     values = c("Peak_cfs"=16, "Daily_cfs"=17, "PeakEst"=NA, 
                                "DailyEst" = NA)) +
  scale_colour_manual(name = "Legend", 
                      labels = c("Obs 15-min", "Obs 24-hour", "15-min P3", "24-hr P3"),
                      values = c("Peak_cfs"="grey", "Daily_cfs"="black", "PeakEst"="dark grey", 
                                 "DailyEst" = "black")) +
  scale_linetype_manual(name = "Legend",
                        labels = c("Obs 15-min", "Obs 24-hour", "15-min P3", "24-hr P3"),
                        values = c("Peak_cfs"="blank", "Daily_cfs"="blank", "PeakEst"="solid",
                                   "DailyEst" = "dashed"))+
  guides(colour = guide_legend(override.aes = list(
    linetype = c("blank", "blank", "solid", "dashed"),
    shape = c(16,17,NA,NA),
    color = c("grey","black", "dark grey", "black")))) +
  theme(legend.position=c(0.8, 0.6),  
    legend.background = element_rect(fill="white"),
    legend.key = element_blank(),
    legend.box = "horizontal")
#> Warning: Removed 12 rows containing missing values (geom_point).

ggplot2: Creating a legend which includes multiple symbols, line types, and colors

2 Answers