Should number of records in combo be 2 rather than 3?
Why _N_=1 make the minimal record rule not applicable?
data a;
input x 1. y $2.;
datalines;
1 A
5 T
;
data b;
input x 1. z $2.;
datalines;
1 F
3 R
2 G
;
data combo;
if _N_=1 then set a;
set b;
run;
Even more surprizing if dataset a contains only one observation.
To help understand , try
data combo;
put _n_;
if 1 then set a;
set b;
run;
and then change 1 for 0. Trying this, I conclude that the datastep stops iterating as soon as one of the set or input statements hits an end of file.
PG
data combo;
if _N_=1 then set a;
set b;
run;proc print;run;
Result is :
1 | A | F | |
3 | A | R | |
2 | A | G |
data combo2;
put _n_;
if 1 then set a;
set b;
run; proc print;run;
result is:
1 | A | F | |
3 | T | R |
Why is this different?
The datastep loop iterates as long as it can. When a set statement tries to read beyond end of file, the loop continues to the end, it does not produce a new observation, and it stops.
In the first case, set a is prevented from reading beyond the end of file, so it is set b that tries first.
In the second case, set a is read at every loop, so it tries to read beyond the end of file first.
PG
Or most instructive, try:
data b;
input x 1. z $2.;
datalines;
1 F
3 R
;
data combo;
put "Before " _n_ (_all_) (=);
if not endOfB then set b end=endOfB;
put "After " _n_ (_all_) (=);
if _n_ > 5 then stop;
run;
Intricate...
PG
PG's code
data combo;
if 1 then set a;
set b;
run;
is the same with the following code:
data combo;
set a;
set b;
run;
Because A is the smallest table ,so when Data Step reach at the end of A, it
stop working.You only can get two observations.
Ksharp
SAS stops when it reaches the end of a dataset. In your example, the end of dataset SAS reaches is the end of dataset b. " if _n_=1 then set data a;" makes it impossible for SAS to reach the end of dataset a.
Here is a classic paper on this whole topic what you may find helpful:
http://www.lexjansen.com/nesug/nesug88/sas_supervisor.pdf
Haikuo
Are you ready for the spotlight? We're accepting content ideas for SAS Innovate 2025 to be held May 6-9 in Orlando, FL. The call is open until September 16. Read more here about why you should contribute and what is in it for you!
Learn how use the CAT functions in SAS to join values from multiple variables into a single value.
Find more tutorials on the SAS Users YouTube channel.
Select SAS Training centers are offering in-person courses. View upcoming courses for: