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: Use lattice graphics to create a density estimate for the variable uptake. Create the plot in such a way that you get a separate plot for every combination of type and treatment. Make sure the plots of the same type are in the same column. Store the graph in an object called p9.

 

Note: The command as.grob() from the ggplotify package enables Dodona to check your result. Just put your ordinary graphical command(s) between the two comments.