code: function convertA1toR1C1 (ref) {
    if (!A1.test(ref)) {
      throw new Error(`${ref} is not a valid A1 cell reference`)
    }
  
    var refParts = ref
      .replace(A1, '$1,$2')
      .split(',')
  
    var columnStr = refParts[0]
    var row = refParts[1]
    var column = 0
  
    for (var i = 0; i < columnStr.length; i++) {
      column = 26 * column + columnStr.charCodeAt(i) - 64
    }
  
    return `R${row}C${column}`
  }
docs: Convert A1 notation to R1C1 notation
  
  @param   {String} ref
  @returns {String}
  @throws  {Error}