Contributor
Posts: 33

# check if a character is an alphabet

Suppose I have one character variable with length = 1 and I want to check if the value is an alphabet only.

Below is my code.Let me know if you have handier code.

data t2;

set  t1;

if var1 in ("A","B","C","D", "E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y", "Z") then ind = 1;

else ind = 0;

run;

PROC Star
Posts: 8,163

## Re: check if a character is an alphabet

Do you only want to check for uppercase characters?  Otherwise you could use:

data t2;

set t1;

ind=anyalpha(var1);

run;

if you really are only interested in upper case characters, you could use:

data t2;

set t1;

ind=anyupper(var1);

run;

Super Contributor
Posts: 1,636

## Re: check if a character is an alphabet

data t1;
input var1 \$;
cards;
a
b
2
5
t
r
;
data t2;

set  t1;

ind=ifn(lengthn(compress(var1,,'ka'))=1,1,0);

run;
proc print;run;

Contributor
Posts: 30

## Re: check if a character is an alphabet

Another option is using regular expressions:

data t2;

set t1;

one_alpha_rx=prxparse("/[a-zA-Z]/");

ind=prxmatch(one_alpha_rx,x);

drop one_alpha_rx;

run;

For the problem you describe, you'd be better off using Art and Linlin's solutions - they're simpler and probably faster. But if you have to check more complex patterns some time, it's worth learning about regexp matching (this webform won't let me copy and paste, but there's a good paper on this in the SUGI29 archives).

As an example of where regexp comes in handy, I had an application where ID variables were expected to be twelve digits followed by an alpha character and then four more digits. To check whether inputs fit this rule, I used:

legal_pattern=prxparse("/\d{12}[a-zA-Z]\d{4}/");

Note that regexp matching doesn't check whether the variable EXACTLY matches the pattern defined, only whether it appears somewhere in there. But this isn't a problem if the length of the regexp exactly matches the length of the variable.

Super Contributor
Posts: 339

## Re: check if a character is an alphabet

Hi,

HTH

Regards,

Amir.

Occasional Contributor
Posts: 10

Contributor
Posts: 30

## Re: check if a character is an alphabet

Toby, have you tested that PrxMatch code? When I use that one I'm getting zeroes where they shouldn't be.

Occasional Contributor
Posts: 10