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qqline connects the first and third quartiles. How do I draw a line between different quantiles (ie 30% and 70%)?
I have a qqnorm plot of a data set with 1000+ points. I want to draw a line between two quantiles at a time (say 30% and 70%) just as qqline does with 25% and 75%, but with the freedom of choosing which quantiles to use. I've poked around with ggplot a bit but can't seem to get something that works. What's the best way to do this?
I've found a function that seems to do what I want, called plot.qqline in the package sma. Unfortunately, this is a really old package and is now deprecated. However, that's the type of functionality I'm looking for.
edit: Figured it out!