Sys.setenv(PLOTLY_MATHJAX_PATH="/opt/mathjax")
# PLOTLY_MATHJAX_PATH 环境变量指向 MATHJAX

x = seq(from = -4, to = 8, length.out = 193)
y1 = dnorm(x, mean = 3, sd = 1)
y2 = dnorm(x, mean = 2, sd = 1.5)
library(magrittr)
hline <- function(y = 0, color = "red") {
  list(
    type = "line",
    x0 = 0,
    x1 = 1,
    xref = "paper",
    y0 = y,
    y1 = y,
    line = list(color = color, dash = 'dash')
  )
}

vline <- function(x = 0, color = "red") {
  list(
    type = "line",
    x0 = x,
    x1 = x,
    yref = "paper",
    y0 = 0,
    y1 = 1,
    line = list(color = color, dash = 'dash')
  )
}

p = plotly::plot_ly(
  x = x, y = y1,
  type = "scatter", mode = "lines",
  fill = "tozeroy", fillcolor = "rgba(92, 184, 92, 0.2)",
  text = ~ paste0(
    "x：", x, "<br>",
    "y：", round(y1, 3), "<br>"
  ),
  hoverinfo = "text",
  name = plotly::TeX("\\mathcal{N}(3,1^2)"),
  line = list(shape = "spline", color = "#5CB85C")
) %>%
  plotly::add_trace(
    x = x, y = y2,
    type = "scatter", mode = "lines",
    fill = "tozeroy", fillcolor = "rgba(91, 192, 222, 0.2)",
    text = ~ paste0(
      "x：", x, "<br>",
      "y：", round(y2, 3), "<br>"
    ),
    hoverinfo = "text",
    name = plotly::TeX("\\mathcal{N}(2, 1.5^2)"),
    line = list(shape = "spline", color = "#5BC0DE")
  ) %>%
  plotly::layout(
    xaxis = list(showgrid = F, title = plotly::TeX("x")),
    yaxis = list(showgrid = F, title = plotly::TeX("f(x)")),
    legend = list(x = 0.8, y = 1, orientation = "v")
  ) %>%
  plotly::config(displayModeBar = FALSE, mathjax = "local")

# 导出静态图形
plotly::orca(p, file = "plot.png", mathjax = T)

报如下错误

Error in mathjax_local() : 
  Couldn't locate necessary MathJax config: TeX-AMS-MML_SVG

把 mathjax_local 函数翻出来看了下

plotly:::mathjax_local

function () 
{
    path <- mathjax_path()
    mj <- file.path(path, "MathJax.js")
    if (!file.exists(mj)) 
        stop("Couldn't locate MathJax.js")
    mathjax <- readLines(mj)
    pat <- "MathJax.fileversion=\"[0-9].[0-9].[0-9]"
    ver <- regmatches(mathjax, regexpr(pat, mathjax))
    ver <- sub("\"", "", strsplit(ver, "=")[[1]][2])
    config <- file.path(path, "config", "TeX-AMS-MML_SVG.js")
    if (!file.exists(config)) 
        stop("Couldn't locate necessary MathJax config: TeX-AMS-MML_SVG")
    htmltools::htmlDependency(name = "mathjax", version = ver, 
        src = path, script = c("MathJax.js", "config/TeX-AMS-MML_SVG.js"))
}
<bytecode: 0x7fd92d6ecb98>
<environment: namespace:plotly>

MathJax config 是什么东西呢？MathJax ( https://github.com/mathjax/MathJax ) 找不到 TeX-AMS-MML_SVG.js

参考

https://plotly-r.com/mathjax.html