[英]How to reverse inverse hyperbolic sine transformation in R?
使用反雙曲正弦變換的變換可以使用這個簡單的函數在R中完成:
ihs <- function(x) {
y <- log(x + sqrt(x ^ 2 + 1))
return(y)
}
但是,我找不到扭轉這種轉變的方法。 所以我的問題是:如何反轉R中的反雙曲正弦變換?
@ Maju116給出了正確答案,但他沒有展示他的作品。 :-)
下面是如何推導反雙曲正弦函數的逆與完整的R解一起生成函數和圖。
y = \log(x + \sqrt{x^2 + 1})
\exp(y) - x = \sqrt{x^2 + 1}
Squaring both sides
\exp(2y) + x^2 - 2\exp(y)x = x^2 + 1
\exp(2y) - 1 = 2\exp(y)x
(1/2)*(\exp(2y) - 1)/exp(y) = x
library(ggplot2)
# inverse hyperbolic since function
ihs <- function(x) {
y <- log(x + sqrt(x^2 + 1))
return(y)
}
# hyperbolic sine function
hs = function(x) {
0.5*exp(-x)*(exp(2*x) - 1)
}
# data
dfX = data_frame(x = seq(-2, 2, 0.01),
ihs = ihs(x),
hs1 = sinh(x),
hs2 = hs(x))
# plot
ggplot(data = dfX, aes(x = x)) +
stat_function(aes(color = "Inverse Hyperbolic Sine"), fun = ihs, ) +
stat_function(aes(color = "Hyperbolic Sine (Manual)"), fun = hs) +
stat_function(aes(color = "Hyperbolic Sine (Base)"), fun = sinh) +
theme_bw() +
scale_colour_manual("Function", values = c("red", "darkblue", "darkgreen"))][1]][1]
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