如何在R中画出y轴两边几乎相同的函数?

I have a function that depends on distance and behaves different according to the direction (east or west) to where you evaluate it. Now I have two plots side by side, but I need to have them as one, where the labels of the axis are shared and the x axis label is centered. Here is an example of how the code looks right now:I have a function that depends on distance and