Hello, Is there a way for R to determine the point where a confidence interval equals a specified value? For example:
x = seq(1:5) y = c(5, 5, 4, 4, 3) lm = lm(y ~ x) p = predict.lm(lm, interval="confidence") matplot(p, type="b") abline(h = 3) I want to answer the question: "What is the value of x when the y-value of the lower confidence interval is equal to 3.0"? Visually, it is the place on the example where the abline intersects the lower confidence interval, or about 4.2. Can R calculate this number for me? I know that predict.lm will calculate a y-value from an x-value, but what I want is the opposite. I know the y-value, and I want to calculate the x-value. Larry Howe ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
