library(ggplot2)

#dataframe
ID <- 1:12
series2 <- runif(12, min=4, max=15)
series1 <- runif(12, min=25, max=50)
df <- data.frame(ID, series1, series2)

#graph1
ggplot(df) + 
  geom_col(aes(ID, series1), size = 1, color = "darkblue", fill = "white") +
  scale_x_continuous(breaks=seq(1, 12, 1))

#graph2
ggplot(df) +
  geom_line(aes(ID, series2), size = 1.5, color="red") +
  scale_x_continuous(breaks=seq(1, 12, 1))


#add graph2 to graph1
ggplot(df) + 
  geom_col(aes(ID, series1), size = 1, color = "darkblue", fill = "white") +
  geom_line(aes(ID, series2), size = 1.5, color="red")+
  scale_x_continuous(breaks=seq(1, 12, 1))


#multiply by 2
ggplot(df) + 
  geom_col(aes(ID, series1), size = 1, color = "darkblue", fill = "white") +
  geom_line(aes(ID, 2*series2), size = 1.5, color="red") +
  scale_x_continuous(breaks=seq(1, 12, 1))

#set the axis divided by 2
ggplot(df) + 
  geom_col(aes(ID, series1), size = 1, color = "darkblue", fill = "white") +
  geom_line(aes(ID, 2*series2), size = 1.5, color="red") +
  scale_x_continuous(breaks=seq(1, 12, 1)) +
  scale_y_continuous(sec.axis = sec_axis(~./2))

#add secondary y-axis title
ggplot(df) + 
  geom_col(aes(ID, series1), size = 1, color = "darkblue", fill = "white") +
  geom_line(aes(ID, 2*series2), size = 1.5, color="red") +
  scale_x_continuous(breaks=seq(1, 12, 1)) +
  scale_y_continuous(sec.axis = sec_axis(~./2, name = "series2"))