Problem ordering columns in barplot

General
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1

Hi! I have been working on some grouped barplots using ggplot2 and had an issue with the order of the columns. The plot shows them in alphabetical order (August, July, June, May, September) instead of chronological order. Any idea on how to fix it? Here is my code and plot:

ggplot(aes(x=Date, y=Mean_PLWP, group=Species, fill=Species), data=MeanWaterPotDawnX)+
+geom_bar(position="dodge", stat="identity")+
+ylim(0, 1) +
+labs(title = "Mean PLWP per month and species",
+x = "Month of measurement",
+y = "PLWP (MPa)")

image
image859×644 10.7 KB

Thanks a lot!

2 
ggplot(aes(x=Date, y=Mean_PLWP, group=Species, fill=Species), data=MeanWaterPotDawnX) +
  geom_bar(position="dodge", stat="identity") +
  ylim(0, 1) +
  labs(title = "Mean PLWP per month and species",
       x = "Month of measurement",
       y = "PLWP (MPa)") +
  scale_x_discrete(limits=c("May", "June", "July", "August", "September"))
3

Thank you very much! It works perfectly.