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标题: SAS--Perl Regular Expressions(正则表达式) [打印本页]

作者: shiyiming 时间: 2010-10-22 22:32
标题: SAS--Perl Regular Expressions(正则表达式)
From SAS_Miner's blog on Sina

正则表达式基础
正则表达式由一些普通字符和一些元字符（metacharacters）组成。普通字符包括大小写的字母和数字，而元字符则具有特殊的含义（详细内容查help）。
一个正则表达式，就是用某种模式去匹配一类字符串的一个公式。
很多人因为它们看上去比较古怪而且复杂所以不敢去使用，这些复杂的表达式其实写起来还是相当简单的，而且，一旦你弄懂它们，你就能把数小时辛苦而且易错的文本处理工作压缩在几分钟（甚至几秒钟）内完成。
 
1、PRXMATCH
(regular-expression_r_r_r-id | perl-regular-expression_r_r_r,
source)
data
_null_;
  
position=prxmatch('/world/', 'Hello world!');
   put
position=;
run;
 
2、PRXCHANGE(perl-regular-expression_r_r_r |
regular-expression_r_r_r-id, times, source)
data
_NULL_;
   
x="fejiwof'wefji'f''fe";
   
y=prxchange("s/'/M/",-1,x); 
 
run;
 
3、data
_null_;
   
text='aaaa111 bbb222ccc333 444dd55';
   
y=prxchange('s/(\d)([a-z])|([a-z])(\d)/$1$3*$2$4/',-1,text);
   
put
y;                
      
run;
Results: 
  aaaa*111 bbb*222*ccc*333
444*dd*55
 
4.
Remove spaces in the add field that separate a single alphabetic
character and a string of numerical digits (1 or many)
 
 c 32
->c32
add=prxchange("s/(\b[A-Za-z])\s(\d+\b)/$1$2/",-1,add)
 
数字与字母间插入空格：
bbb222ccc333 
->bbb 222 ccc 333 
 
addr=prxchange('s/(\d)([A-Za-z])|([A-Za-z])(\d)/$1$3
$2$4/',-1,add)
 
 
 具体用法 SAS HELP
<table CELLSPACING="0" CELLPADDING="0" BORDER="1">
<tbody>
<tr>
<td VALIGN="top" WIDTH="28%">
[a-z]
</TD>
<td VALIGN="top" WIDTH="71%">
specifies a range of
characters that matches any character in the range:
<ul TYPE="disc">
<li>"[a-z]" matches any lowercase alphabetic
character in the range "a" through "z"</LI>
</UL>
 
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
[^a-z]
</TD>
<td VALIGN="top" WIDTH="71%">
specifies a range of
characters that does not match any character in the
range:
<ul TYPE="disc">
<li>"[^a-z]" matches any character that is
not in the range "a" through "z"</LI>
</UL>
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\b
</TD>
<td VALIGN="top" WIDTH="71%">
matches a word boundary (the
position between a word and a space):
<ul TYPE="disc">
<li>"er\b" matches the "er" in
"never"</LI>
<li>"er\b" does not match the "er" in
"verb"</LI>
</UL>
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\B
</TD>
<td VALIGN="top" WIDTH="71%">
matches a non-word
boundary:
<ul TYPE="disc">
<li>"er\B" matches the "er" in
"verb"</LI>
<li>"er\B" does not match the "er" in
"never"</LI>
</UL>
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\d
</TD>
<td VALIGN="top" WIDTH="71%">
matches a digit character
that is equivalent to [0-9].
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\D
</TD>
<td VALIGN="top" WIDTH="71%">
matches a non-digit character
that is equivalent to [^0-9].
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\s
</TD>
<td VALIGN="top" WIDTH="71%">
matches any white space
character including space, tab, form feed, and so on, and is
equivalent to [\f\n\r\t\v].
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\S
</TD>
<td VALIGN="top" WIDTH="71%">
matches any character that is
not a white space character and is equivalent to
[^\f\n\r\t\v].
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\t
</TD>
<td VALIGN="top" WIDTH="71%">
matches a tab character and
is equivalent to "\x09".
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\w
</TD>
<td VALIGN="top" WIDTH="71%">
matches any word character
including the underscore and is equivalent to
[A-Za-z0-9_].
</TD>
</TR>
<tr>
<td VALIGN="top" WIDTH="28%">
\W
</TD>
<td VALIGN="top" WIDTH="71%">
matches any non-word
character and is equivalent to [^A-Za-z0-9_].
</TD>
</TR>
</TBODY>
</TABLE>
 
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