How do I determine length of variable

[sri1]

Hi all,

I have the following sample code and want to create the variable "Name" with maximum length of strings in variable name instead of default $200 and I would like the length to be updated when the dataset changes.Is there anyway I can do in datastep?

data attrs;
dsid=open("sashelp.class", "i"); 
n_vars=attrn(dsid, "nvars");
do i=1 to n_vars;
Name=varname(dsid, i);
Type=vartype(dsid, i);

output;

end;

rc=close(dsid);

run;

Your solutions are highly appreciated.

Thanks

[rudfaden]

Not that elegant. But it works.

Save the max length of name in a macro.

data attrs;
dsid=open("sashelp.class", "i"); 
n_vars=attrn(dsid, "nvars");
do i=1 to n_vars;
Name=varname(dsid, i);
Type=vartype(dsid, i);

output;
call symput('len',max(length(name)));

end;
rc=close(dsid);
run;

Alter the length of the column.

proc sql;
alter table attrs
  modify Name char(&len);
quit;

[mkeintz]

I would assign a fixed length of $32 to the variable name, since that is the maximum allowable  length of any sas variable name.

See Rules for most SAS names 

[Tom]

Why does it matter what length the variable has, as long as the length is not too SHORT?

proc sql noprint;
  select max(length(NAME)) into :max_length trimmed
  from sashelp.class
  ;
quit;

data class ;
  length name $&max_length. ;
  set sashelp.class;
run;

[rudfaden]

If a variable is to long it will use unessesary space and SAS will run slower. Not a big deal if you have small dataset. But if you have billions of rows it matters.

[mkeintz]

Question:   Are you trying the determine the longest length of all the varnames (that is my assumption)?   Or are you trying to determine the longest value of a variable called NAME?

[sri1]

@mkeintz  You are right.I am trying to  determine the longest length of all the varnames

[sri1]

@TomThanks for your reply.I am trying to determine the maximum length of all the varnames but not NAME column of sashelp.class

[Tom]

---

@sri1 wrote:

@TomThanks for your reply.I am trying to determine the maximum length of all the varnames but not NAME column of sashelp.class

---

Huh?  Why?  What are you going the change once you know that information?

The maximum length of a SAS variable name is 32 bytes.

Anyway the method to find the max is the same, only use as input the DICTIONARY metadata tables instead of the actual data.

[sri1]

@Tom I know that  maximum length of a SAS variable name is 32 bytes but to reduce the storage space.

[mkeintz]

@sri1 

I can see the benefit of reducing the length of a variable from $200 to $32, just as a matter of good housekeeping, if nothing else. And if you were to load your resulting data set  into memory (via the SASFILE statement or via a hash  object) you could save a meaningful amount of memory for a large collection.

But  I don't see nearly as much value in trying to cut down from $32, to (say) $15 based on the varnames actually in use.  Using $32 guarantees you always will have allocated enough space, and also means you don't have to inspect all the metadata in order to establish the absolute minimum necessary length.

[TomKari]

Consider using compression. I had a similar situation where I couldn't predict character variable length, and some outliers were VERY long, and when I used the compression option it reduced the overhead to a very manageable amount.

Tom