For the following questions you work with the built-in dataset CO2. It contains data on the CO2 uptake in two types of grassplants (Quebec and Mississippi), and this with two different treatments (chilled and not chilled):

 

   Plant   Type  Treatment conc uptake
1    Qn1 Quebec nonchilled   95   16.0
2    Qn1 Quebec nonchilled  175   30.4
3    Qn1 Quebec nonchilled  250   34.8
4    Qn1 Quebec nonchilled  350   37.2
5    Qn1 Quebec nonchilled  500   35.3
6    Qn1 Quebec nonchilled  675   39.2
7    Qn1 Quebec nonchilled 1000   39.7
8    Qn2 Quebec nonchilled   95   13.6
9    Qn2 Quebec nonchilled  175   27.3
10   Qn2 Quebec nonchilled  250   37.1

 

Question: Finally, use ggplot2 graphics to create a barplot with the mean uptake for every concentration, and add an error bar giving the 95% confidence interval around the mean. Use a grey scale to fill the bars and color the error bars based on concentration. You can start with a grey value of 0.7 and end with a grey value of 0.

Add a title saying “Mean uptake per concentration”, remove the label of the Y axis and add a label “Concentration” to the X axis. As the mean uptake for a concentration of 95 differs significantly from the rest, also add three stars (***) above the first bar. Store the graph in an object called p11.

 

Note: Because Dodona can check ggplot2 graphics directly, we do not need the ggplotify package and you can immediately start typing your graphical command(s).