Transcript Debugging SAS Programs

Debugging SAS Programs
Finding and Correcting
Errors
Checking the Log
• It is always a good idea to check the log
file.
• Start at the beginning of the log file, and
correct the first error. Sometimes one
mistake can create many errors.
Errors, Warnings, and Notes
• There are three kinds of notifications that SAS inserts
into log files: Errors, Warnings, and Notes.
• An Error indicates that there was a problem in the
program and SAS could not execute the program.
.
• A Warning indicates that there was a problem in the
program, but SAS figured out how to continue.
• Notes can indicate that a program worked as planned or
that a program worked differently.
Some Notes are very important!
Backwards Illustrations
• When your SAS programs don’t work the
way that you want, you’ll have to figure out
what went wrong.
• In this lesson, errors will be introduced
intentionally to see the results.
Missing Semicolons
• Missing semicolons are the most common
mistake to make.
• From Program 4, if:
DATA weight;
INFILE 'C:\SAS_Files\tomhs.dat';
• Is replaced with:
DATA weight
INFILE 'C:\SAS_Files\tomhs.dat';
One Missing Semicolon Produced:
ERROR: No DATALINES or INFILE statement.
ERROR: Extension for physical file name
"C:\SAS_Files\tomhs.data" does not correspond to
a valid member type.
NOTE: The SAS System stopped processing this step
because of errors.
WARNING: The data set WORK.WEIGHT may be
incomplete. When this step was stopped there
were 0 observations and 8 variables.
WARNING: The data set WORK.INFILE may be
incomplete. When this step was stopped there
were 0 observations and 8 variables.
How to figure out what happened:
• The Error said that there wasn’t a
DATALINES or INFILE statement, but you
know that there was one.
• SAS must not have identified the INFILE
statement as an INFILE statement.
• Checking the code shows that that SAS
thought that the INFILE statement was
part of the DATA statement because a
semicolon was missing.
Another Missing Semicolon:
• From Program 4, if:
PROC FREQ DATA=weight;
TABLES sex clinic ;
TITLE 'Frequency Distribution of Clinical Center
and Gender';
• Is replaced with:
PROC FREQ DATA=weight;
TABLES sex clinic
TITLE 'Frequency Distribution of Clinical Center
and Gender';
The Missing Semicolon Produced:
------------------------------------------------------22
200
ERROR: Variable TITLE not found.
ERROR 22-322: Syntax error, expecting one of the
following: a name, ;, (, *, -, /, :,
_ALL_, _CHARACTER_, _CHAR_,
_NUMERIC_.
ERROR 200-322: The symbol is not recognized
and will be ignored.
How to figure out what happened:
• SAS says that the variable TITLE wasn’t
found.
• You know that TITLE isn’t a variable.
• SAS must think that TITLE is part of a list
of variables.
• There is no semicolon separating TITLE
from the variables SEX and CLINIC!
Unbalanced Quotation Marks
• An Unbalanced quotation marks warning can
indicate that a quotation mark is missing.
• From Program 5, if:
DATA tdata;
INFILE 'C:\SAS_Files\tomhs.data’;
• Is replaced with:
DATA tdata;
INFILE 'C:\SAS_Files\tomhs.data;
One Missing Quotation Mark
Produced:
WARNING: The quoted string currently being processed
has become more than 262 characters long. You may
have unbalanced quotation marks.
861 ;
850 INFILE 'C:\SAS_Files\tomhs.data;
------------------------49
NOTE 49-169: The meaning of an identifier after a quoted
string may change in a future SAS release. Inserting
white space between a quoted string and the succeeding
identifier is recommended.
What if you Balance the Quotation
and Run Again?
• You still get errors!
• SAS interprets your program as a
continuation of the program it ran before.
Since there is an unbalanced quote, your
quotes are still unbalanced and you get
the Note:
NOTE 49-169: The meaning of an identifier after a quoted string may change in
a future SAS release. Inserting white space between a quoted string and
the succeeding identifier is recommended.
The Fix: Another Unbalance Quote
• Run these two lines of code:
‘
RUN;
• Do this ONCE (so the unbalance quote
becomes balanced).
• You program should run properly now (as
long as it is error-free).
Another Fix
•
•
•
•
•
This may be easier to understand:
First, correct the unbalanced quote.
Second, save your SAS program.
Third, exit SAS.
Fourth, reopen SAS and run your saved
program.
Invalid Data
• If SAS is expecting a number, but gets text
instead, you can get invalid data notes.
• From Program 5, if:
@ 12 clinic
$1.
• Is replaced with:
@ 12 clinic
1.
One Missing $ Produced:
NOTE: The infile 'C:\SAS_Files\tomhs.dat' is:
File Name=C:\SAS_Files\tomhs.dat,
RECFM=V,LRECL=256
NOTE: Invalid data for clinic in line 1 12-12.
RULE: ----+----1----+----2----+----3----+----4----+----5----+----6----+----7----+---1
C03615 C 11/10/1987 5 51 1 1 06/26/1936 5 4 2
71.5 05/17/1988
11/25/
80 1988 205.5 199.0
093 084 143 138 36 36 5 260 046
111
159
4.8 063 02213 45.6 9.3 46.4 00471 00711 03611 01906 0.0
00 1
238 1 1 1 2 1 1 1 1 1 1
ptid=C03615 clinic=. group=5 sex=1 educ=4 evsmoke=2 alcbl=0 sebl_1=1
sebl_6=1 _ERROR_=1
_N_=1
Mixing up PROCs
• Different PROCs have different options.
• From Program 5, if:
PROC FREQ DATA=tdata;
TABLES clinic group sex educ sebl_1 sebl_6;
• Is replaced with:
PROC FREQ DATA=tdata;
VAR clinic group sex educ sebl_1 sebl_6;
Using the Wrong Syntax Produced:
1015 PROC FREQ DATA=tdata;
1016 VAR clinic group sex educ sebl_1
sebl_6;
--180
ERROR 180-322: Statement is not valid or it
is used out of proper order.
• Note: Similar errors can be produced by
missing semicolons
Misspelled Variable in a PROC
• From Progam 4, if:
PROC FREQ DATA=weight;
TABLES sex clinic ;
• Is replaced with:
PROC FREQ DATA=weight;
TABLES sex clinc ;
• You get:
ERROR: Variable CLINC not found.
Uninitialized Variables
• From Program 4, if:
bmi = (weight*703.0768)/(height*height);
• Is replaced with:
bmi = (wieght*703.0768)/(height*height);
• You get:
NOTE: Variable wieght is uninitialized.
What’s an Uninitialized Variable?
• An uninitialized variable is a variable that
SAS considers to be nonexistent.
• This usually occurs when a variable name
on the RHS of an equation is misspelled.
• In the example, the error was caused by a
misspelling—SAS had no variable called
wieght.
Forgetting the RUN Statement
• If you forget the RUN statement at the end
of you program, SAS will not run (on PC)
• You won’t get any output.
• You may not get any errors or warnings.
Fix: Run a single RUN; statement.
Catching Errors as You Write:
• You don’t have to write an entire program,
then run the whole thing.
• Try writing your programs in stages.
– Write part and run it.
– If your program works, write the next part, and
run it.
– If your program produced errors or warnings,
it must have been from the last part that you
wrote.
Multipart Programs
• If you are writing a program in stages, you may
have multiple procedures. Running the same
procedures over and over produces a lot of
output and log files to check.
• Once you get a procedure to work, you can
enclose it in a comment (/* . . . */) while you work
on other procedures.
• Just remove the comment when you’ve finished
the whole program.
Example:
DATA weight;
INFILE 'C:\SAS_Files\tomhs.dat';
INPUT @1 ptid $10. @12 clinic $1. @27 age 2. @30 sex 1.
@58 height 4.1 @85 weight 5.1 @140 cholbl;
bmi = (weight*703.0768)/(height*height);
RUN;
/*
PROC FREQ DATA=weight;
TABLES sex clinic ;
TITLE 'Frequency Distribution of Clinical Center and Gender';
RUN;
*/
PROC FREQ DATA=weight;
TABLES clinic/ NOCUM ;
TITLE 'Frequency Distribution of Clinical Center ';
TITLE2 '(No Cumulative Percentages) ';
RUN;
*Now SAS will only perform the second PROC FREQ;
Checking On Your Data Sets
• Sometimes your data steps don’t work the way
you want, but there aren’t any clear indications
of problems from the log file.
• You can insert a PROC PRINT to see your data:
PROC PRINT DATA=mydata;
RUN;
• Then, when you’re sure that your data is OK,
you can either delete the PROC PRINT or
convert it into a comment:
*PROC PRINT DATA=mydata;
*RUN;