functions for processing maths expressions

R/eq.R

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+#' Insert an equation.
+#'
+#' @param eqs Character. The path to the equation text file, or a data frame of the equations.
+#' @param number integer. The number of the equation.
+#' @param label Character. The label of the equation.
+#' @param style character. The style of the equation.
+#' @param skip integer. nteger: the number of lines of the data file to skip before beginning to read data.
+#'
+#' @return A string of the equation.
+#' @export
+#' @examples eq()
+eq <- function(eqs = NULL, label = NULL, number = NULL,
+               style = c('numbered', 'display', 'inline', 'none'),
+               skip = 6) {
+  if(is.null(eqs)) return(message('A source file of the equations must be give.'))
+  if(is.null(number) & is.null(label)) return(message('A number of label of the equation must be given.'))
+  style <- match.arg(style)
+  latex_label <- ifelse(is.null(label), number, label)
+  before <- switch (style,
+                    numbered = paste0('\\begin{equation}\n'),
+                    display = '$$',
+                    inline = '$',
+                    none = NULL
+  )
+  after <- switch (style,
+                   numbered = paste0('\n  (\\#eq:', latex_label, ')\n\\end{equation}'),
+                   display = '$$',
+                   inline = '$',
+                   none = NULL
+  )
+
+  if(!is.data.frame(eqs)) eqs <- read_eq(eqs, skip)
+  eq_txt <- ifelse(is.null(number), eqs$eq[eqs$label == label], eqs$eq[eqs$n == number])
+  cat(before, eq_txt, after, sep = '')
+}
+
+#' Read equations from a file
+#'
+#' @param eqs character. The path of the equation file.
+#' @param skip integer. the number of lines of the data file to skip before beginning to read data.
+#'
+#' @return a data frame with equations
+#' @export
+#'
+#' @examples
+#' eq_file <- paste0(system.file(package = 'rosr'), '/skeleton/equation/rosr-eq.Rmd')
+#' eqs <- read_eq(eq_file)
+read_eq <- function(eqs, skip){
+  eqs <- read.table(eqs, skip = skip, sep = '|', header = TRUE,
+                    stringsAsFactors = FALSE, encoding = 'UTF-8')
+  eqs <- eqs[-1, c("number", "label", "description", "eq" )]
+  eqs$eq <- gsub('^[[:space:]]*[\\$]*', '', eqs$eq)
+  eqs$eq <- gsub('[\\$]*[[:space:]]*$', '', eqs$eq)
+  eqs$number <- rm_space(eqs$number)
+  eqs$label <- rm_space(eqs$label)
+  return(eqs)
+}