Helpers to Compose Equations with Eqn — Eqn

These functions extend Eqn to facilitate composing LaTeX equations with desirable features and pleasant typography.

Eqn_overset and Eqn_underset typesets a label over or under a LaTeX expression or a "latexMatrix" object
Eqn_overbrace and Eqn_underbrace typesets a brace, with an optional label over or under an object
Eqn_newline, Eqn_hspace and Eqn_vspace facilitate spacing of parts of an equation.
Eqn_size changes size of LaTeX text; Eqn_text includes a literal string in equations.

Each of these (except Eqn_text) have aliases without the Eqn_ prefix for brevity.

For example, given the matrix A = matrix(1:4), 2, 2), the call Eqn(overset(A, "A")) generates:


\overset{\mathbf{A}}
 { \begin{pmatrix}
  1 & 3 \
  2 & 4 \
  \end{pmatrix}
 }

When rendered in LaTeX, this produces: $$ \overset{\mathbf{A}} { \begin{pmatrix} 1 & 3 \\ 2 & 4 \\ \end{pmatrix} } $$

You can also use these for straight LaTeX expressions, such this equation showing and labeling the Hat matrix in regression. See the examples for the call to underbrace for this. $$\mathbf{\hat{y}} = \underbrace{\mathbf{X}(\mathbf{X}^{\top}\mathbf{X})^{-1} \mathbf{X}^{\top}}_{\mathbf{\mathbf{H}}}\mathbf{y}$$

Eqn_newline() emits a newline (\) in an equation, with an optional increase to the padding following the newline.

Eqn_text() inserts a literal string to be rendered in a text font in an equation.

Eqn_hspace() is used to create (symmetric) equation spaces, most typically around = signs Input to lhs, rhs can be a numeric to increase the size of the space or a character vector to be passed to the LaTeX macro \hspace{}.

Eqn_vspace() inserts vertical space between lines in an equation. Typically used for aligned, multiline equations.

Eqn_size() is used to increase or decrease the size of LaTeX text and equations. Can be applied to a specific string or applied to all subsequent text until overwritten.

Usage

overset(
  x,
  label,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

underset(
  x,
  label,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

overbrace(
  x,
  label = NULL,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

underbrace(
  x,
  label = NULL,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

Eqn_overset(
  x,
  label,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

Eqn_underset(
  x,
  label,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

Eqn_overbrace(
  x,
  label = NULL,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

Eqn_underbrace(
  x,
  label = NULL,
  label.style = c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " ")
)

Eqn_newline(space = 0)

newline(space = 0)

Eqn_text(text)

Eqn_hspace(lhs = 5, mid = "", rhs = NULL, times = 1)

hspace(lhs = 5, mid = "", rhs = NULL, times = 1)

Eqn_vspace(space)

vspace(space)

Eqn_size(string, size = 0)

size(string, size = 0)

Arguments

x: a numeric or character matrix, or a character string LaTeX expression or a "latexMatrix" object
label: a character string used as the label above or below the object x. If missing, and a "matrix" object was passed, it's name is used as the label. In LaTeX, these are rendered in a size appropriate for superscripts and subscripts, but you can use a size modifier to change this, for example '\Large{"A"}'.
label.style: The name of a math font used to to typeset the label. One of c("mathbf", "mathrm", "mathit", "mathsf", "mathcal", "mathtt", " "). The default, "mathbf" wraps the label inside "\mathbf{ }" commonly used for the name of a matrix.
space: includes extra vertical space. Metric of the vertical space must be 'ex', 'pt', 'mm', 'cm', 'em', 'bp', 'dd', 'pc', or 'in'
text: argument to be used within \text{}
lhs: spacing size. Can be a number between -1 and 6. -1 provides negative spaces and 0 gives no spacing. Input can also be a character vector, which will be passed to \hspace{} (e.g., '1cm'; see space argument for supported metrics). Default is 5, resulting in a \quad space.
mid: character vector to place in the middle of the space specification. Most commonly this will be operators like '='
rhs: see lhs for details. If left as NULL and mid is specified the this will be set to rhs to create symmetric spaces around mid
times: number of times to repeat the spacings
string: a string that should have its text size modified. If missing the size modifier is returned, which applies the size modifier to the remainder of the text until reset with Eqn_size()
size: numeric size of LaTeX text modifier, ranging from -3 (\tiny) to 5 (\HUGE), with 0 defining the normal test size (\normalsize; default)

Value

Returns a character vector containing the LaTeX expressions for the given operation. You can pass this to cat to display the result on the console, or include it inside a call to Eqn to typeset it.

Author

Michael Friendly, Phil Chalmers

Examples

library(matlib)
A <- matrix(1:4, 2, 2)
B <- matrix(4:1, 2, 2)
AB <- A + B
Eqn(overset(A, "A"))
#> 
#> \begin{equation*}
#> \overset{\mathbf{A}} 
#> { \begin{pmatrix} 
#> 1 & 3 \\ 
#> 2 & 4 \\ 
#> \end{pmatrix}
#>  }
#> \end{equation*}
  #  missing label: uses the name of the object
Eqn(overset(A))
#> 
#> \begin{equation*}
#> \overset{\mathbf{A}} 
#> { \begin{pmatrix} 
#> 1 & 3 \\ 
#> 2 & 4 \\ 
#> \end{pmatrix}
#>  }
#> \end{equation*}

# test just a character LaTeX expression
Eqn('a', overset('=', '?'), 'b')
#> 
#> \begin{equation*}
#> a\overset{\mathbf{?}} 
#> { = }
#> b\end{equation*}

# a labelled latexMatrix equation
Eqn(overset(A, "A"), "+",
    overset(B, "B"), "=",
    underset(AB, "A+B"))
#> 
#> \begin{equation*}
#> \overset{\mathbf{A}} 
#> { \begin{pmatrix} 
#> 1 & 3 \\ 
#> 2 & 4 \\ 
#> \end{pmatrix}
#>  }
#> +\overset{\mathbf{B}} 
#> { \begin{pmatrix} 
#> 4 & 2 \\ 
#> 3 & 1 \\ 
#> \end{pmatrix}
#>  }
#> =\underset{\mathbf{A+B}} 
#> { \begin{pmatrix} 
#> 5 & 5 \\ 
#> 5 & 5 \\ 
#> \end{pmatrix}
#>  }
#> \end{equation*}
    
 # using a LaTeX expression as the label  
 Lambda <- latexMatrix("\\lambda", nrow=2, ncol=2,
                       diag=TRUE)
 Eqn(overset(Lambda, "\\Lambda"))
#> 
#> \begin{equation*}
#> \overset{\mathbf{\Lambda}} 
#> { \begin{pmatrix} 
#>   \lambda_{1} & 0           \\ 
#>   0           & \lambda_{2} \\ 
#> \end{pmatrix}
#>  }
#> \end{equation*}

 # generate LaTeX expression for the Hat matrix, label as "H"
H <- "\\mathbf{X} (\\mathbf{X}^{\\top}\\mathbf{X})^{-1} \\mathbf{X}^{\\top}"
Eqn("\\mathbf{\\hat{y}} =", underbrace(H, "\\mathbf{H}"), "\\mathbf{y}")
#> 
#> \begin{equation*}
#> \mathbf{\hat{y}} =\underbrace{\mathbf{X} (\mathbf{X}^{\top}\mathbf{X})^{-1} \mathbf{X}^{\top}}_{\mathbf{\mathbf{H}}}\mathbf{y}\end{equation*}

# Combine this with overbrace
Eqn(overbrace(underbrace(H, "\\mathbf{H}"), "\\LARGE\\mathbf{\\hat{y}}"))
#> 
#> \begin{equation*}
#> \overbrace{\underbrace{\mathbf{X} (\mathbf{X}^{\top}\mathbf{X})^{-1} \mathbf{X}^{\top}}_{\mathbf{\mathbf{H}}}}^{\mathbf{\LARGE\mathbf{\hat{y}}}}\end{equation*}


Eqn_newline()
#> [1] " \\\\ \n"
Eqn_newline('10ex')
#> [1] " \\\\[10ex] \n"

# more complete example  
Eqn(underset("\\mathbf{X}", "(4 \\times 3)"), "& = \\mathbf{U} \\mathbf{\\Lambda} \\mathbf{V}^\\top",
    Eqn_newline('1ex'),
    ' & =',
    latexMatrix("u", 4, 3),
    latexMatrix("\\lambda", 3, 3, diag=TRUE),
    latexMatrix("v", 3, 3, transpose = TRUE),
    align=TRUE)
#> 
#> \begin{align*}
#> \underset{\mathbf{(4 \times 3)}} 
#> { \mathbf{X} }
#> & = \mathbf{U} \mathbf{\Lambda} \mathbf{V}^\top \\[1ex] 
#>  & =\begin{pmatrix} 
#>   u_{11} & u_{12} & u_{13} \\ 
#>   u_{21} & u_{22} & u_{23} \\ 
#>   u_{31} & u_{32} & u_{33} \\ 
#>   u_{41} & u_{42} & u_{43} \\ 
#> \end{pmatrix}
#> \begin{pmatrix} 
#>   \lambda_{1} & 0           & 0           \\ 
#>   0           & \lambda_{2} & 0           \\ 
#>   0           & 0           & \lambda_{3} \\ 
#> \end{pmatrix}
#> \begin{pmatrix} 
#>   v_{11} & v_{12} & v_{13} \\ 
#>   v_{21} & v_{22} & v_{23} \\ 
#>   v_{31} & v_{32} & v_{33} \\ 
#> \end{pmatrix}^\top
#> \end{align*}



Eqn_hspace()
#> [1] "\\quad"
Eqn_hspace(3) # smaller
#> [1] "\\;"
Eqn_hspace(3, times=2)
#> [1] "\\;\\;"
Eqn_hspace('1cm')
#> [1] "\\hspace{1cm}"

# symmetric spacing around mid
Eqn_hspace(mid='=')
#> [1] "\\quad=\\quad"
Eqn_hspace(mid='=', times=2)
#> [1] "\\quad\\quad=\\quad\\quad"


Eqn_vspace('1.5ex')
#> [1] " \\vspace{1.5ex} \n"
Eqn_vspace('1cm')
#> [1] " \\vspace{1cm} \n"



# set size globally
Eqn_size(size=3)
#> [1] "\\LARGE"
Eqn_size() # reset
#> [1] "\\normalsize"

# locally for defined string
string <- 'e = mc^2'
Eqn_size(string, size=1)
#> [1] "{\\large e = mc^2}"