Testing the rOpenSci {katex} package

test-katex.Rmd

---
title: "Testing rOpenSci katex"
author: "Jesus M. Castagnetto"
date: "2021-07-12"
output: 
  html_document:
    mathjax: null
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE, comment = "")
library(katex)
```

## Tests

Equations from: https://www.intmath.com/cg5/katex-mathjax-comparison.php



```{r}
tex1 <- "\\frac{1}{\\Bigl(\\sqrt{\\phi \\sqrt{5}}-\\phi\\Bigr) e^{\\frac25 \\pi}} \\equiv 1+\\frac{e^{-2\\pi}} {1+\\frac{e^{-4\\pi}} {1+\\frac{e^{-6\\pi}} {1+\\frac{e^{-8\\pi}} {1+\\cdots} } } }"
eq1 <- katex_html(tex1, include_css = TRUE)
```

Equation 1: `r eq1`

```{r}
tex2 <- "\\left( \\sum_{k=1}^n a_k b_k \\right)^2 \\leq \\left( \\sum_{k=1}^n a_k^2 \\right) \\left( \\sum_{k=1}^n b_k^2 \\right)"
eq2 <- katex_html(tex2, include_css = FALSE)
```

Equation 2: `r eq2`

```{r}
tex3 <- "1 +  \\frac{q^2}{(1-q)}+\\frac{q^6}{(1-q)(1-q^2)}+\\cdots = \\prod_{j=0}^{\\infty}\\frac{1}{(1-q^{5j+2})(1-q^{5j+3})}, \\text{ for }\\lvert q\\rvert < 1."
eq3 <- katex_html(tex3, include_css = FALSE)
```

Equation 3: `r eq3`

```{r}
tex4 <- "\\int u \\frac{dv}{dx}\\,dx=uv-\\int \\frac{du}{dx}v\\,dx"
eq4 <- katex_html(tex4, include_css = FALSE)
```

Equation 4: `r eq4`

```{r}
tex5 <- "S (\\omega)=\\frac{\\alpha g^2}{\\omega^5} \\,e ^{[-0.74\\bigl\\{\\frac{\\omega U_\\omega 19.5}{g}\\bigr\\}^{-4}]}"
eq5 <- katex_html(tex5, include_css = FALSE)
```

Equation 5: `r eq5`

## A bit more complex latex environments need mathml

The following **Mathml** output works in Firefox, but not on the Brave or Chromium browsers.

```{r}
tex6 <- "f(n) = \\begin{cases} \\frac{n}{2}, & \\text{if } n\\text{ is even} \\\\ 3n+1, & \\text{if } n\\text{ is odd} \\end{cases}"
eq6 <- katex_mathml(tex6, include_css = FALSE)
```

Equation 6: `r eq6`


```{r}
tex7 <- "\\begin{aligned}
\\dot{x} & = \\sigma(y-x) \\\\ 
\\dot{y} & = \\rho x - y - xz \\\\ 
\\dot{z} & = -\\beta z + xy 
\\end{aligned}"
eq7 <- katex_mathml(tex7, include_css = FALSE)
```

Equation 7: `r eq7`

```{r}
tex8 <- "\\begin{pmatrix} 
a_{11} & a_{12} & a_{13}\\\\ 
a_{21} & a_{22} & a_{23}\\\\ 
a_{31} & a_{32} & a_{33} 
\\end{pmatrix}"
eq8 <- katex_mathml(tex8, include_css = FALSE)
```

Equation 8: `r eq8`

This solution to this issue was resolved by @jeroen in the gist https://gist.github.com/jeroen/3209a68bc7d1b1562e8234b154d7ab6b, and the issue related to this ropensci/katex#3 was fixed in the commit ropensci/katex@44f0f45