Feature request: Nice Matrix support

[fyuniv]

There is a LaTeX package NiceMatrix that is similar to tabular but support nice matrix output. For example, one may add row and/or indices, and add colors, draw vertical or horizontal line segments. I think typst-tablex is totally cable of producing nicer matrix. The following is an example.

#import "@preview/tablex:0.0.6": *
#tablex(
  columns: (auto, 3pt,)+(auto,)*3+(3pt,), 
  auto-lines: false, 
  align: center + horizon,
  map-cells: cell => {
    cell.content = {show math.equation: set text(0.8em); cell.content}
    if cell.x == 0 {cell.content = text(red, cell.content)}
    if cell.y == 0 {cell.content = text(blue, cell.content)}
    cell
    },
  [], [],  $C_1$,$ C_2$, $C_3$, [],
  $R_1$, rowspanx(2)[$lr("(", size: #300%)$], $a_11$, $a_12$, $a_13$, rowspanx(2)[$lr(")", size: #300%)$],
  $R_2$, $a_21$, $a_22$, $a_23 + a_(12)$,
)

Is it possible that typst-tablex provides an function that similar to the original mat() function, but can easily place the delimiter after the $k$-th column below the $j$-th row?

[PgBiel]

Hi! Indeed, seems like tablex could be helpful to simulate matrices, though I'm not yet sure to which extent that should be supported by default. Perhaps that could become a separate package? Not sure. But it's certainly possible to investigate.

Regarding the delimiter, can you show a sample ideal tablex (or other function) call with your proposed parameters / functions / other kinds of API, and then show the expected output? That could be helpful for some initial design discussion. Thanks!

[fyuniv]

I don't know how to effectively slice and arrange an array of matrix entries so that tablex will produce a desired matrix. Maybe define a function matx as follows

#let matx(delim: "(", row-index:true, column-index: true, dimension: (3,3), row-color:(1, red), column-color: (1, blue), align: center + horizon, auto-lines: false, array) = {
  $
  tablex(
    columns: if column-index {(auto,)+(3pt,)+(auto,)*columns+(3pt,)} else {(3pt,)+(auto,)*9+(3pt,)}, 
    auto-lines: auto-line, 
    align: align,
    map-cells: cell => {
      cell.content = {show math.equation: set text(0.8em); cell.content}
      if cell.x == row-color.at(0) {cell.content = text(row-color.at(1), cell.content)}
      if cell.y == column-color.at(0) {cell.content = text(column-color.at(1), cell.content)}
      cell
      },
      // codes that arrange the matrix array to get the desired outlook
    )
  $
}

Then produce a matrix by calling

#matx(
[], [],  $C_1$,$ C_2$, $C_3$, [],
  $R_1$, $a_11$, $a_12$, $a_13$, 
  $R_2$, $a_21$, $a_22$, $a_23 + a_(12)$,
)

Sorry that I couldn't provide an working example.

[PgBiel]

Thanks for the suggestion. I'll definitely consider adding this at some point.