ggplot legend of multiples lines/points/bar plot

Question

So, I'm having trouble with the legend of a multiple line/point/bar plot. Just the lines appears and I couldn't change its names neither add the bar element to it, here's the code I´m running:

df.rain %>% 
  ggplot(aes(x = date))+
  labs(y = "Rain (mm); Temperature (°C)")+
  geom_bar(aes(y = P_mm), 
           fill = "honeydew4",
           stat = "identity",
           width = 5)+ 

  geom_point(aes(y = T_max), shape = 2)+
  geom_line(aes(y = T_max, linetype = "dashed"))+
  geom_point(aes(y = T_min), shape = 3)+
  geom_line(aes(y = T_min, linetype = "solid"))+
  geom_point(aes(y = DPV_d*15), shape = 1)+
  geom_line(aes(y = DPV_d*15, linetype = "dotted"))+
  scale_y_continuous(sec.axis = sec_axis(trans = ~ . /15 , 
                                         name = "DPV (kPa)"))+ 
  scale_x_date(date_breaks = "2 month",
               date_minor_breaks = "1 month",
               date_labels = "%b %Y") +
  theme_bw() +
  theme(axis.title.x = element_blank()) 

And the results:

Answer 1

Here is a possible solution, with mock data :

EDIT: : I added two lines to control legend labels :

1. mutate(variable = factor(fct_relevel(variable, "T_min", "T_max", "DPV_d", "P_mm"))) : where you define the order
2. geom_blank() : correct ordering with a blank geom at first.

PLOT:

Code:

library(tidyverse)

w_dat <- tibble(date = seq(as.Date("2017-01-01"), 
                       as.Date("2017-12-01"), 
                       by = "month"),
                P_mm = sample(20:150, 12, replace = TRUE),
                T_max = sample(15:30, 12, replace = TRUE),
                T_min = T_max * sample(seq(0.5, 0.9, 0.05), 12, replace = TRUE),
                DPV_d = sample(seq(0.5, 2, 0.1), 12, replace = TRUE))

w_dat %>% 
  mutate(DPV_d = DPV_d * 15) %>%
  gather(variable, value, -date) %>%
  mutate(variable = factor(fct_relevel(variable, "T_min", "T_max", "DPV_d", "P_mm"))) %>% 
  ggplot(data = ., aes(x = date, y = value, shape = variable, linetype = variable, fill = variable)) +
  geom_blank() +
  geom_bar(data = . %>% filter(variable == "P_mm"),
       stat = "identity",
       width = 5) + 
  geom_point(data = . %>% filter(variable != "P_mm")) +
  geom_line(data = . %>% filter(variable != "P_mm")) +
  labs(y = "Rain (mm); Temperature (°C)") +  
  scale_y_continuous(sec.axis = sec_axis(trans = ~ . /15 , 
                                     name = "DPV (kPa)")) + 
  scale_x_date(date_breaks = "2 month",
           date_minor_breaks = "1 month",
           date_labels = "%b %Y") +
  theme_bw() +
  theme(axis.title.x = element_blank()) +
  scale_shape_manual("The legend you want", 
                 values = c("T_min" = 3,
                            "T_max" = 2,
                            "DPV_d" = 1,
                            "P_mm" = NA)) +
  scale_linetype_manual("The legend you want",
                    values = c("T_min" = "solid",
                               "T_max" = "dashed",
                               "DPV_d" = "dotted",
                               "P_mm" = "blank")) +
  scale_fill_manual("The legend you want",
                values = c("T_min" = "white",
                           "T_max" = "white",
                           "DPV_d" = "white",
                           "P_mm" = "honeydew4"))

Answer 2

Not exactly what I was looking for, couldn't merge point and linetpe, but manage to produce a meaningful legend

df.rain %>% 
  ggplot(mapping = aes(x = date))+
  labs(y = "Rain (mm); Temperature (°C)")+
  geom_bar(aes(y = P_mm, fill = "Chuva"),
           stat = "identity",
           width = 5)+ 

  geom_point(aes(y = T_max, shape = "tmax"))+
  geom_line(aes(y = T_max), linetype = "dashed")+
  geom_point(aes(y = T_min, shape = "tmin"))+
  geom_line(aes(y = T_min), linetype = "solid")+
  geom_point(aes(y = DPV_d*45, shape = "dpv"))+
  geom_line(aes(y = DPV_d*45), linetype = "dotted")+
  scale_y_continuous(sec.axis = sec_axis(trans = ~ . /45 , 
                                         name = "DPV (kPa)"))+ 
  scale_x_date(date_breaks = "2 month",
               date_minor_breaks = "1 month",
               date_labels = "%b %Y") +
  scale_fill_manual(name = "", values = c("Chuva" = "honeydew4")) +
  scale_shape_manual(name = "", values = c("tmax" = 2, "tmin" = 3, "dpv" = 1), labels = c("T° max", "T° min", "DPV")) +
  theme_bw() +
  theme(axis.title.x = element_blank(),
        axis.text.x = element_text(angle = 45, vjust = 1, 
                                   size = 9, hjust = 1),
        legend.position = "bottom",
        legend.text = element_text(size = 8),
        legend.box.background = element_rect(),
        legend.box.margin = margin(0.6, 0.6, 0.6, 0.6))