GGplot2 plotting fitted lines

Hi amazing Rstudio community

I'm having a problem with ggplot2 and the fitted lines
I want to have a sharp fitted line line you can get with the standard plot function in R. However, my ggplot2 won't allow this and it only gives a smooth fitted line. Please see the one graph (which shows the line that I want - but on ggplot2 and not the standard R package) and if anyone can help me, I would really appreciate it.

Thank you.


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