Try this: approx(p[,"lwr"], 1:5, 3)
On 6/2/06, Larry Howe <[EMAIL PROTECTED]> wrote: > 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 > ______________________________________________ [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
