在 R 中找到给定 f(x) 的曲线的 x 值？

Question

我想知道为什么我找不到 x 的另一个现有值，其 f(x) 等于 f(.6)?

也就是说，我想知道如何找到下图中红色X所指示的点的x值？

这是我尝试过但没有成功的方法：

source("https://raw.githubusercontent.com/rnorouzian/i/master/ii.r") # source the function

f <- function(x, n.pred = 5, N = 100, conf.level = .95){ 
  ci <- R2.ci(R2 = x, n.pred = n.pred, N = N, conf.level = conf.level)  # The objective function
  ci$upper - ci$lower
}

curve(f, panel.f = abline(v = .6, h = f(.6), col = 2, lty = c(2, 1)))  # curve the function

uniroot(function(x) f(.6) - f(x), c(0, 1))[[1]]  # find the requested 'x' value

`Error: f() values at end points not of opposite sign`

Answer 1

 abline(v=uniroot(function(x) f(.6) - f(x), c(0, 0.4))[[1]])

在 R 中找到给定 f(x) 的曲线的 x 值？

Finding the x value of a curve given f(x) in R?

math

optimization

r

function

linear-algebra