In friendly/matlib: Matrix Functions for Teaching and Learning Linear Algebra and Multivariate Statistics

This is from: StackOverflow

Uses knitr::knit_print() to define methods for printing objects of class "matrix".

# Define a generic method that transforms an object x in a LaTeX string
as_latex = function(x, ...) {
  UseMethod('as_latex', x)
}

# Define a class latex for LaTeX expressions
as_latex.character = function(x) {
  structure(
    paste(x, collapse = ' '), 
    class = c('latex', 'character')
  )
}

# A character string of class latex is rendered in display mode
# Define a knit_print() method for the latex class
knit_print.latex = function(x, ...) {
  knitr::asis_output(
    paste0('$$', x, '$$')
  )
} 

# Now, define a method as_latex for matrix
as_latex.matrix = function(x, ...) {
  as_latex(c(
    '\\begin{bmatrix}',
    paste(
      t(x),
      rep(c(rep('&', nrow(x) - 1), '\\\\'), ncol(x)),
      collapse = ''
    ),
    '\\end{bmatrix}'
  ))
}

# Indicate to knitr that matrix are rendered as latex
knit_print.matrix = function(x, ...) {
  knitr::knit_print(as_latex(x))
}

# Build a knitr inline hook to display inline latex in inline mode
default_inline_hook = knitr::knit_hooks$get('inline')
knitr::knit_hooks$set(inline = function(x) {
  x = paste(gsub('\\$\\$', '$', x))
  default_inline_hook(x)
})

A = matrix(c(1,3,0,1),2,2)
B = matrix(c(5,3,1,4),2,2)

Now, matrix are rendered as LaTeX:

Matrix A in inline mode: r A

Matrix A in display mode:

A

Operators

As other answers suggested, it could be useful to define operators.
With the previous class, it is relatively straightforward:

`%times%` = function(x, y) {
  as_latex(sapply(list(x, '\\times', y), as_latex))  
}

`%add%` = function(x, y) {
  as_latex(sapply(list(x, '+', y), as_latex))  
}

Example in inline mode: r A %add% A %times% B

Display mode:

A %times% B

friendly/matlib documentation built on Dec. 6, 2024, 9:25 a.m.