Graphics Reference
In-Depth Information
Figure 4-1. Basic line graph
Discussion
In this sample data set, the xvariable,
Time
, is in one column and the yvariable,
demand
, is in
another:
BOD
Time demand
1
8.3
2
10.3
3
19.0
4
16.0
5
15.6
7
19.8
Line graphs can be made with discrete (categorical) or continuous (numeric) variables on the x-
axis. In the example here, the variable
demand
is numeric, but it could be treated as a categorical
you must also use
aes(group=1)
to ensure that
ggplot()
knows that the data points belong