今天遇到一个问题，如果字符串中既有字母又有数字，如何将数字删除，将字母保留下来？
之后发现compress不仅可以将字符串中空格删掉，加了modifier后也可以实现指定字符的删除。
于是对compress的用法做了一个总结，不全，欢迎补充～

data test;

string="ABC abcdef($1234)";

noblanks=compress(string);              /*去除字符串中的空格*/

nonum=compress(string,,'d');           /*去除字符串中的数字*/

nonumblank=compress(string,,'ds');/*去除字符串中的数字以及空格*/

nochar=compress(string,,'a');            /*去除字符串中所有字母*/

noabc1=compress(string,'ABC');       /*去除ABC三个大写字母*/

noabc2=compress(string,'abc','i');    /*此处加了条件i，忽略大小写，不论大小写，都将abc去除*/

nosign=compress(string,,'p');            /*去除字符串中的符号*/

nosignnum=compress(string,,'pd'); /*去除符号以及数字*/

retaina=compress(string,'a','ki');     /*不论大小写，将字符串中a字母保留下来，其他全都删掉*/

run;

结果如下：

下面是SAShelp中列出的Compress Modifier和说明：

a or A

addsalphabetic characters to the list of characters.

c or C

addscontrol characters to the list of characters.

d or D

addsdigits to the list of characters.

f or F

adds theunderscore character and English letters to the list of characters.

g or G

addsgraphic characters to the list of characters.

h or H

adds ahorizontal tab to the list of characters.

i or I

ignoresthe case of the characters to be kept or removed.

k or K

keeps thecharacters in the list instead of removing them.

l or L

addslowercase letters to the list of characters.

n or N

addsdigits, the underscore character, and English letters to the list ofcharacters.

o or O

processesthe second and third arguments once rather than every time the COMPRESSfunction is called. Using the O modifier in the DATA step (excluding WHEREclauses), or in the SQL procedure, can make COMPRESS run much faster when youcall it in a loop where the second and third arguments do not change.

p or P

addspunctuation marks to the list of characters.

s or S

addsspace characters (blank, horizontal tab, vertical tab, carriage return, linefeed, form feed, and NBSP ('A0'x, or 160 decimal ASCII) to the list ofcharacters.

t or T

trimstrailing blanks from the first and second arguments.

u or U

addsuppercase letters to the list of characters.

w or W

addsprintable characters to the list of characters.

x or X

addshexadecimal characters to the list of characters.

更多例子：

Example1：

x='123-4567-8901B 234-5678-9012 c';

y=compress(x,'ABCD', 'l');

put y;

123-4567-8901234-5678-9012

Example2：

x='1    2   3    4    5';

y=compress(x,, 's');

put y;

12345

Example3：

x='Math AEnglish B Physics A';

y=compress(x,'ABCD', 'k');

put y;

ABA

Example4：

x=' ';

l=lengthn(compress(x));

put l;

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