r - Ploting two plots (3 variables) with one x-axes in ggplot

Question

I am trying to plot two flows and one rainfall data in one graph. I have broke it up into top and bottom parts as shown in the following pic. Here I have two issues with thi

Answer 1

As an explanation of what @pierre means... turn your data from "wide" to "long" format using reshape2::melt, so that the flow type for each date is in one column flow_type, and the value is another (flow_val). Then you specify flow_type as the grouping variable with which to assign colour:

require(reshape2)

x.melted <- melt(x, id.vars = c("date", "rain"), variable.name="flow_type",
                 value.name="flow_val")

g.bottom <- ggplot(x.melted, aes(x = date),size=0.5) +
  geom_linerange(aes(ymin=0, ymax=flow_val, colour=flow_type)) +  #plot flow
  labs(x = "Date", y = "River flow (ML/day)") +
  theme_classic() +
  theme(plot.background = element_rect(fill = "transparent"),
        plot.margin = unit(c(2,0,1,1),units="lines"), 
        legend.position="bottom") + 
  scale_colour_manual(guide = guide_legend(title = "Flow Type"), 
                      values = c("obsflow"="blue", "simflow"="red"))