在ggplot2中添加stat_smooth到只有一个facet。

I have some data for which, at one level of a factor, there is a significant correlation. At the other level, there is none. Plotting these side-by-side is simple. Adding a line to both of them with stat_smooth, also straightforward. However, I do not want the line or its fill displayed in one of the two facets. Is there a simple way to do this? Perhaps specifying a blank color for the fill and colour of one of the lines somehow? I have some data for which, at one level of a f