accessing data of the plot within ggtitle

Question

I am wondering if it is somehow possible to access the columns of the provided data within a ggplot2 graph for the title. So something like that:

gg         


        

Answer 1

I would try the following as it is not possible to pipe outside aes().

ggplot(mpg %>% filter(manufacturer == 'audi'), 
       aes(x = hwy, y = displ, label = model)) + 
  geom_point() + 
  geom_text(data = . %>% filter(hwy > 28)) +
  facet_wrap(~manufacturer)+
  theme(strip.background = element_blank(),
        strip.text = element_text(hjust = 0, size = 14))

The idea is to use a facet with empty strip background. If there are more names or variables one has to create an extra faceting variable using e.g. mutate(gr = "title")

mpg %>% 
  mutate(title="This is my plot") %>% 
ggplot(aes(x = hwy, y = displ, col=manufacturer)) + 
  geom_point() + 
  facet_wrap(~title)+
  theme(strip.background = element_blank(),
        strip.text = element_text(hjust = 0, size = 14))

Edit

As you asked a second question here are two solutions for creating individual plots for each group

# first solution
p <- mpg %>%
  group_by(manufacturer) %>% 
     do(plots= ggplot(., aes(cyl, displ)) +
      geom_point() + 
      ggtitle(unique(.$manufacturer))
   )
p %>% slice(1) %>% .$plots


# second solution
mpg %>%
  nest(-manufacturer) %>%
  mutate(plot = map2(data, manufacturer, ~ggplot(data=.x,aes(cyl, displ))+
           geom_point() +
           ggtitle(.y))) %>% 
  slice(1) %>% .$plot 

Or save the data using

map2(paste0(p$manufacturer, ".pdf"), p$plots, ggsave)