R/unit-conversions.R

In sportyR: Plot Scaled 'ggplot' Representations of Sports Playing Surfaces

#' Convert all units, regardless of starting and ending units
#'
#' @param meas A measurement in any unit of length
#' @param from_unit A string containing the original unit of measure to be
#'   converted
#' @param to_unit A string containing the ending unit of measure
#' @param conversion_columns A vector containing the columns to convert if
#'   \code{meas} is of type \code{data.frame}
#'
#' @return The measurement in converted units
#'
#' @export
#'
#' @examples
#' convert_units(1, "in", "cm")
#' convert_units(100, "cm", "m")
convert_units <- function(meas,
                          from_unit,
                          to_unit,
                          conversion_columns = NULL) {
  # Convert the from_unit and to_unit to be lower case
  from_unit <- tolower(from_unit)
  to_unit <- tolower(to_unit)

  # Create the conversion table
  conversion_table <- data.frame(
    unit_name = c(
      "millimeters",
      "centimeters",
      "meters",
      "inches",
      "feet",
      "yards"
    ),
    unit_abbreviation = c(
      "mm",
      "cm",
      "m",
      "in",
      "ft",
      "yd"
    ),
    conversion_factor = c(
      304.8,
      30.48,
      0.3048,
      12,
      1,
      1 / 3
    )
  )

  # Ensure that the from_unit and to_unit exist somewhere in the conversion
  # table
  if (!(from_unit %in% conversion_table$unit_abbreviation) &&
      !(from_unit %in% conversion_table$unit_name)) {
    stop(glue::glue("{from_unit} is not a viable unit at this time."))
  }

  if (!(to_unit %in% conversion_table$unit_abbreviation) &&
      !(to_unit %in% conversion_table$unit_name)) {
    stop(glue::glue("{to_unit} is not a viable unit at this time."))
  }

  # This function should work over entire data frames as well as individual
  # vectors
  if (is.data.frame(meas)) {

    # If no columns are supplied, alert user of error
    if (is.null(conversion_columns)) {
      stop(glue::glue("Must supply columns to convert"))
    }

    # Iterate over the supplied columns and perform the conversion
    for (column in conversion_columns) {
      # Check to ensure the column name is in the data frame's column names
      if (!(column %in% names(meas))) {
        message(
          glue::glue(
            "{column} is not a column in the supplied data frame. Skipping..."
          )
        )
      } else if (class(meas[, column]) %in% c("integer", "numeric")) {
        # Columns must be either integer or numeric in type
        if (from_unit %in% conversion_table$unit_abbreviation &&
            to_unit %in% conversion_table$unit_abbreviation) {
          meas[column] <- meas[column] /
            conversion_table[
              conversion_table$unit_abbreviation == from_unit,
              "conversion_factor"
            ]
          meas[column] <- meas[column] *
            conversion_table[
              conversion_table$unit_abbreviation == to_unit,
              "conversion_factor"
            ]
        } else if (from_unit %in% conversion_table$unit_abbreviation &&
                   to_unit %in% conversion_table$unit_name) {
          meas[column] <- meas[column] /
            conversion_table[
              conversion_table$unit_abbreviation == from_unit,
              "conversion_factor"
            ]
          meas[column] <- meas[column] *
            conversion_table[
              conversion_table$unit_name == to_unit,
              "conversion_factor"
            ]
        } else if (from_unit %in% conversion_table$unit_name &&
                   to_unit %in% conversion_table$unit_abbreviation) {
          meas[column] <- meas[column] /
            conversion_table[
              conversion_table$unit_name == from_unit,
              "conversion_factor"
            ]
          meas[column] <- meas[column] *
            conversion_table[
              conversion_table$unit_abbreviation == to_unit,
              "conversion_factor"
            ]
        } else {
          meas[column] <- meas[column] /
            conversion_table[
              conversion_table$unit_name == from_unit,
              "conversion_factor"
            ]
          meas[column] <- meas[column] *
            conversion_table[
              conversion_table$unit_name == to_unit,
              "conversion_factor"
            ]
        }
      } else {
        # If a supplied column is neither of type integer or numeric, alert user
        # that the column is
        message(glue::glue("{column} is not convertable. Skipping..."))
      }
    }

    # Return the data frame
    return(meas)
  } else {
    # Perform the conversion by first converting the input into the base unit,
    # then converting to the desired unit
    if (from_unit %in% conversion_table$unit_abbreviation &&
        to_unit %in% conversion_table$unit_abbreviation) {
      reduced <- meas /
        conversion_table[
          conversion_table$unit_abbreviation == from_unit,
          "conversion_factor"
        ]
      result <- reduced *
        conversion_table[
          conversion_table$unit_abbreviation == to_unit,
          "conversion_factor"
        ]
    } else if (from_unit %in% conversion_table$unit_abbreviation &&
               to_unit %in% conversion_table$unit_name) {
      reduced <- meas /
        conversion_table[
          conversion_table$unit_abbreviation == from_unit,
          "conversion_factor"
        ]
      result <- reduced *
        conversion_table[
          conversion_table$unit_name == to_unit,
          "conversion_factor"
        ]
    } else if (from_unit %in% conversion_table$unit_name &&
               to_unit %in% conversion_table$unit_abbreviation) {
      reduced <- meas /
        conversion_table[
          conversion_table$unit_name == from_unit,
          "conversion_factor"
        ]
      result <- reduced *
        conversion_table[
          conversion_table$unit_abbreviation == to_unit,
          "conversion_factor"
        ]
    } else {
      reduced <- meas /
        conversion_table[
          conversion_table$unit_name == from_unit,
          "conversion_factor"
        ]
      result <- reduced *
        conversion_table[
          conversion_table$unit_name == to_unit,
          "conversion_factor"
        ]
    }

    # Return the converted measurement
    return(result)
  }
}