我有 y 与 x 的线图。 y 是 sigmoid,从 0 到 1 变化。
library(tidyverse)
# continuous variables
x <- seq(-5, 5, 0.1)
# compute y1
error_term <- runif(1, min = -2, max = 2)
y1 <- 1/(1 + exp(-x + error_term))
# compute y2
error_term <- runif(1, min = -2, max = 2)
y2 <- 1/(1 + exp(-x + error_term))
# merge y
y <- c(y1, y2)
x <- c(x, x)
# categorical variable
a <- c(rep(0, 101), rep(1, 101))
tbl <- tibble(x, a, y)
# TASK
# 1. determine values of x at which y = 0.5 for all categories and store them in variable x0
# 2. Use x0 to draw vertical lines in plots at x where y is 0.5
# ggplot
ggplot(data = tbl,
aes(x = x,
y = y)) +
geom_line() +
theme_bw() +
facet_grid(a ~ .)
答案 0 :(得分:1)
这真的不是 ggplot 内置的东西,所以你需要在绘图之前自己总结数据。您可以编写一个辅助函数,然后为这些行创建所需的数据
find_intersect <- function(x,y, target=0.5) {
optimize(function(z) (approxfun(x,y)(z)-target)^2, x)$minimum
}
line_data <- tbl %>%
group_by(a) %>%
summarize(xint=find_intersect(x,y))
然后用
绘图ggplot(data = tbl,
aes(x = x,
y = y)) +
geom_line() +
theme_bw() +
geom_vline(aes(xintercept=xint), data=line_data) +
facet_grid(a ~ .)