dual variable plots have one variable using the left vertical axis and the other variable using the right vertical axis. the purpose of these plots is to show a comparison between the two variables, but the two different axes are auto ranging at different values, so the comparison is not meaningful.
For plots with multiple variables, each variable that shares the same unit should share the same axis. It's possible we may want to compare variables with different units and then it would be meaningful to show those with different axes.
dual variable plots have one variable using the left vertical axis and the other variable using the right vertical axis. the purpose of these plots is to show a comparison between the two variables, but the two different axes are auto ranging at different values, so the comparison is not meaningful.
For plots with multiple variables, each variable that shares the same unit should share the same axis. It's possible we may want to compare variables with different units and then it would be meaningful to show those with different axes.