Making line plot with discrete x-axis in ggplot2

Question

I am building a ggplot2 figure with a facet grid. On my Y-axis are percentages, and my X-axis is the concentration (in numbers). Each facet has 3 groups (0, 24 and 48 hours)

Answer 1

On this page they make the following modification df2$dose<-as.factor(df2$dose). You can try to modify your x-axis as df2$Concentration<-as.factor(df2$Concentration)

or like this:

ggplot(data=MasterTable, aes(x=factor(Concentration), y=Percentage, group=Time)) + 
  geom_point() + 
  geom_line() + 
  facet_grid(Chemicals ~ Treatments)