Question

我有以下文字：

This sentence contains a certain date which is 06-08-2003.  
On this date, 29-12-1945 my grandmother was born.  
12-04-1997 was an important year for celebrations.

我想在date函数的变量中获取substr() 似乎不起作用？

Answer 1

您没有向我们展示您的代码，因此我们无法告诉您substr()的错误。也就是说，如果您知道substr()中所需项目的位置，string函数将按预期工作。

在这种情况下，dates出现在每个string内的不同位置。获得所需输出的一种方法是使用strpos()函数来查找连字符是。然后，您可以将其用作参考点来计算每个字符串中date的起始位置：

clear
set obs 3

input str60 string
"This sentence contains a certain date which is 06-08-2003."
"On this date, 29-12-1945 my grandmother was born."
"12-04-1997 was an important year for celebrations."
end

generate new_string = ""

forvalues i = 1 / 3 {
    local pos = strpos(string[`i'], "-") - 2
    replace new_string = substr(string, `pos', 10) in `i'
}


list string new_string

   +-------------------------------------------------------------------------+
   |                                                     string   new_string |
   |-------------------------------------------------------------------------|
1. | This sentence contains a certain date which is 06-08-2003.   06-08-2003 |
2. |          On this date, 29-12-1945 my grandmother was born.   29-12-1945 |
3. |         12-04-1997 was an important year for celebrations.   12-04-1997 |                                                                        
   +-------------------------------------------------------------------------+

此方法假定dates中的strings 一致。也就是说，它们都具有相同的格式并且没有错误。但是，实际上通常情况并非如此。

获得所需输出的更好方法是使用regex和regexs：

generate new_string = regexs(1) + "-" + regexs(2) + "-" + regexs(3)+ regexs(4) if ///
regex(string,"(0[1-9]|[12][0-9]|3[01])[- /.](0[1-9]|1[012])[- /.](19|20)([0-9][0-9])")

以上 正则表达式 不仅可以找到每个date中的每个string，还可以使用一些逻辑条件检查是否前者是有效的。例如：

replace string = "On this date, 29-131945 my grandmother was born." in 2

drop new_string

generate new_string = regexs(1) + "-" + regexs(2) + "-" + regexs(3)+ regexs(4) if ///
regex(string,"(0[1-9]|[12][0-9]|3[01])[- /.](0[1-9]|1[012])[- /.](19|20)([0-9][0-9])")


list string new_string

   +-------------------------------------------------------------------------+
   |                                                     string   new_string |
   |-------------------------------------------------------------------------|
1. | This sentence contains a certain date which is 06-08-2003.   06-08-2003 |
2. |           On this date, 29-131945 my grandmother was born.              |
3. |         12-04-1997 was an important year for celebrations.   12-04-1997 |
   +-------------------------------------------------------------------------+

如您所见，如果第二个date中的string为29-13-1945或29-131945，则相应的观察结果为空。因此，这种方法通常会阻止您获得非感性结果，同时还可以识别有问题的案例。

但请注意，即使这种方法也不是防弹的，您必须通过更改正则表达式来引入额外的灵活性如果你想处理更复杂的案件。

从变量中的每个句子中获取日期

1 个答案: