# Matrix Editor A matrix is a useful way to represent and manipulate linear transformations. They are also used to represent systems of linear equations and many other mathematical structures. Mathfields can display and edit matrices in a variety of ways. ## Creating a Matrix There are several methods to create a matrix in a mathfield. ### Using Keyboard Shortcuts **To create a matrix using the keyboard:** 1. Type a parenthesis, square bracket, or curly brace. 2. Type the first element of the matrix. 3. Type the ALT/OPTION+TAB key to move to the next column: this will automatically transform the expression into a matrix 4. Type the ALT/OPTION+RETURN key to move to the next row. ### Using the Context Menu The mathfield context menu provides a convenient way to create a matrix. **To access the context menu** right click (or CTRL+click) on the mathfield. The menu is also available by typing ALT+SPACE, or by tapping on the menu button in the mathfield. **To insert a matrix using the context menu** select the **Insert Matrix** menu, then select the number of rows and columns of the matrix. ## Matrix Borders The borders of a matrix are parentheses by default. They can be changed to square brackets, curly braces, vertical bars, or none. **To change the border of a matrix** right click (or CTRL+click) on the matrix, then select the desired border from the **Matrix Border** menu. In LaTeX, matrices are represented using the `\\begin\{\}...\\end\{\}` syntax. The argument to the `begin` command determines the type of matrix and is called the **environment**. Inside the environment, the matrix is specified using the `&` character to separate columns and the `\\\\` character to separate rows. The following environments are supported: | Environment | Description | | --- | --- | | `matrix` | A matrix with no delimiters | | `pmatrix` | A matrix surrounded by parentheses | | `bmatrix` | A matrix surrounded by square brackets | | `Bmatrix` | A matrix surrounded by curly braces | | `vmatrix` | A matrix surrounded by vertical bars | | `Vmatrix` | A matrix surrounded by double vertical bars | | `smallmatrix` | A matrix with no delimiters, in a smaller font | | `array` | A matrix with no delimiters, with control over column alignment | --- {` \\begin\{matrix\} a & b \\\\ c & d \\end\{matrix\} `} --- {` \\begin\{pmatrix\} a & b \\\\ c & d \\end\{pmatrix\} `} --- {` \\begin\{bmatrix\} a & b \\\\ c & d \\end\{bmatrix\} `} --- {` \\begin\{Bmatrix\} a & b \\\\ c & d \\end\{Bmatrix\} `} --- {` \\begin\{vmatrix\} a & b \\\\ c & d \\end\{vmatrix\} `} --- {` \\begin\{Vmatrix\} a & b \\\\ c & d \\end\{Vmatrix\} `} --- {` \\begin\{smallmatrix\} a & b \\\\ c & d \\end\{smallmatrix\} `} --- {` \\begin\{array\}\{cc\} a & b \\\\ c & d \\end\{array\} `} ## Changing the Shape of a Matrix **To add or remove rows or columns** right click (or CTRL+click) on the matrix, then select the desired action from the menu. Rows and columns get added or removed relative to the cell the cursor is in. ## Spacing ### Changing the spacing of an individual row The spacing between rows can be adjusted by setting an optional argument to the `\\\\` command. The argument is a length, and can be positive or negative. For example, the following matrix has no space between columns and a double space between rows: {` \\begin\{pmatrix\} a & b \\\\[1.5em] c & d \\end\{pmatrix\} `} Units can be specified using the following abbreviations: - `em` (the width of the letter `M` in the current font) - `mu` (math unit, 1/18 em) - `ex` (the height of the letter `x` in the current font) - `pt` (a point, 1/72.27 inch) - `pc` (a pica, 12 points) - `px` (a pixel, 1/96 inch) - `cm` (a centimeter) - `mm` (a millimeter) - `in` (an inch) - `bp` (a big point, 1/72 inch) - `dd` (a didot point, 1238/1157 mm) - `cc` (a cicero, 12 didot points) - `sp` (a scaled point, 65536 sp = 1 pt) ### Changing the spacing of all rows The spacing between rows can be controlled by setting the `arraystretch` register. The default value is `1.0`. The value of a register can also be modified by using the `\renewcommand` command. In general, modifying registers using `mf.registers` is preferred, but using `\renewcommand` might be handy, for example when rendering static LaTeX. ```json mf.registers.arraystretch = 2.5 ``` {` \\renewcommand\{\\arraystretch\}\{2.5\} \\begin\{pmatrix\} a & b \\\\ c & d \\end\{pmatrix\} `} {` \\renewcommand\{\\arraystretch\}\{0.5\} \\begin\{pmatrix\} a & b \\\\ c & d \\end\{pmatrix\} `}