r - 将 `20` 和 `19` 与整数相加形成日期 `2000`/`1999`

Question

我正在处理以下数据；

这是年度数据，随机样本如下所示；

> sample(years, 10)
 [1] 71 70  8 65 99 15  7  6 63 13

这里 71 对应于 1971 而 15 对应于 2015 - 我想要做的是添加在正确的 19 和正确的 20 日期的最后一位数字之前。所以 8 对应于 2008，99 对应于 1999。任何朝着正确方向的插入都会很棒。
数据从1960年开始，到2017年结束。

数据:

years <- c(60L, 60L, 60L, 60L, 60L, 60L, 60L, 60L, 60L, 60L, 60L, 60L, 
    61L, 61L, 61L, 61L, 61L, 61L, 61L, 61L, 61L, 61L, 61L, 61L, 62L, 
    62L, 62L, 62L, 62L, 62L, 62L, 62L, 62L, 62L, 62L, 62L, 63L, 63L, 
    63L, 63L, 63L, 63L, 63L, 63L, 63L, 63L, 63L, 63L, 64L, 64L, 64L, 
    64L, 64L, 64L, 64L, 64L, 64L, 64L, 64L, 64L, 65L, 65L, 65L, 65L, 
    65L, 65L, 65L, 65L, 65L, 65L, 65L, 65L, 66L, 66L, 66L, 66L, 66L, 
    66L, 66L, 66L, 66L, 66L, 66L, 66L, 67L, 67L, 67L, 67L, 67L, 67L, 
    67L, 67L, 67L, 67L, 67L, 67L, 68L, 68L, 68L, 68L, 68L, 68L, 68L, 
    68L, 68L, 68L, 68L, 68L, 69L, 69L, 69L, 69L, 69L, 69L, 69L, 69L, 
    69L, 69L, 69L, 69L, 70L, 70L, 70L, 70L, 70L, 70L, 70L, 70L, 70L, 
    70L, 70L, 70L, 71L, 71L, 71L, 71L, 71L, 71L, 71L, 71L, 71L, 71L, 
    71L, 71L, 72L, 72L, 72L, 72L, 72L, 72L, 72L, 72L, 72L, 72L, 72L, 
    72L, 73L, 73L, 73L, 73L, 73L, 73L, 73L, 73L, 73L, 73L, 73L, 73L, 
    74L, 74L, 74L, 74L, 74L, 74L, 74L, 74L, 74L, 74L, 74L, 74L, 75L, 
    75L, 75L, 75L, 75L, 75L, 75L, 75L, 75L, 75L, 75L, 75L, 76L, 76L, 
    76L, 76L, 76L, 76L, 76L, 76L, 76L, 76L, 76L, 76L, 77L, 77L, 77L, 
    77L, 77L, 77L, 77L, 77L, 77L, 77L, 77L, 77L, 78L, 78L, 78L, 78L, 
    78L, 78L, 78L, 78L, 78L, 78L, 78L, 78L, 79L, 79L, 79L, 79L, 79L, 
    79L, 79L, 79L, 79L, 79L, 79L, 79L, 80L, 80L, 80L, 80L, 80L, 80L, 
    80L, 80L, 80L, 80L, 80L, 80L, 81L, 81L, 81L, 81L, 81L, 81L, 81L, 
    81L, 81L, 81L, 81L, 81L, 82L, 82L, 82L, 82L, 82L, 82L, 82L, 82L, 
    82L, 82L, 82L, 82L, 83L, 83L, 83L, 83L, 83L, 83L, 83L, 83L, 83L, 
    83L, 83L, 83L, 84L, 84L, 84L, 84L, 84L, 84L, 84L, 84L, 84L, 84L, 
    84L, 84L, 85L, 85L, 85L, 85L, 85L, 85L, 85L, 85L, 85L, 85L, 85L, 
    85L, 86L, 86L, 86L, 86L, 86L, 86L, 86L, 86L, 86L, 86L, 86L, 86L, 
    87L, 87L, 87L, 87L, 87L, 87L, 87L, 87L, 87L, 87L, 87L, 87L, 88L, 
    88L, 88L, 88L, 88L, 88L, 88L, 88L, 88L, 88L, 88L, 88L, 89L, 89L, 
    89L, 89L, 89L, 89L, 89L, 89L, 89L, 89L, 89L, 89L, 90L, 90L, 90L, 
    90L, 90L, 90L, 90L, 90L, 90L, 90L, 90L, 90L, 91L, 91L, 91L, 91L, 
    91L, 91L, 91L, 91L, 91L, 91L, 91L, 91L, 92L, 92L, 92L, 92L, 92L, 
    92L, 92L, 92L, 92L, 92L, 92L, 92L, 93L, 93L, 93L, 93L, 93L, 93L, 
    93L, 93L, 93L, 93L, 93L, 93L, 94L, 94L, 94L, 94L, 94L, 94L, 94L, 
    94L, 94L, 94L, 94L, 94L, 95L, 95L, 95L, 95L, 95L, 95L, 95L, 95L, 
    95L, 95L, 95L, 95L, 96L, 96L, 96L, 96L, 96L, 96L, 96L, 96L, 96L, 
    96L, 96L, 96L, 97L, 97L, 97L, 97L, 97L, 97L, 97L, 97L, 97L, 97L, 
    97L, 97L, 98L, 98L, 98L, 98L, 98L, 98L, 98L, 98L, 98L, 98L, 98L, 
    98L, 99L, 99L, 99L, 99L, 99L, 99L, 99L, 99L, 99L, 99L, 99L, 99L, 
    0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 0L, 1L, 1L, 1L, 1L, 
    1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
    2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
    4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 
    5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 6L, 
    6L, 6L, 6L, 6L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 7L, 
    8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 8L, 9L, 9L, 9L, 9L, 
    9L, 9L, 9L, 9L, 9L, 9L, 9L, 9L, 10L, 10L, 10L, 10L, 10L, 10L, 
    10L, 10L, 10L, 10L, 10L, 10L, 11L, 11L, 11L, 11L, 11L, 11L, 11L, 
    11L, 11L, 11L, 11L, 11L, 12L, 12L, 12L, 12L, 12L, 12L, 12L, 12L, 
    12L, 12L, 12L, 12L, 13L, 13L, 13L, 13L, 13L, 13L, 13L, 13L, 13L, 
    13L, 13L, 13L, 14L, 14L, 14L, 14L, 14L, 14L, 14L, 14L, 14L, 14L, 
    14L, 14L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
    15L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 16L, 
    17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L, 17L)

Answer 1

试试这个:

years + 1900 + 100 * (years <= 18)