SAS: No valid observations are found Error - Simple Regression - sas

Question

I have big panel time series data set. I wish to do this basic SAS regression code:
proc sort data=dataset;
by time_id;
run;
ods output parameterestimates=pe;
proc reg data=dataset;
by time_id;
model y=x1 x2 x3....x15;
quit;
run;
I get this error when I run the code:
ERROR: No valid observations are found.
NOTE: The above message was for the following BY group:
time_id=1
ERROR: No valid observations are found.
NOTE: The above message was for the following BY group:
time_id=2....
Why? My time_id variable exists... is it because I have too many time_id variables? If I select firm_id it works but I want time_id.
Here's a sample of my data (panel time series):
y x firm_id time_id
3.4 100 1 1
2.3 200 1 2
6.5 653 1 3
3 50 2 1
4.34 23 2 2
4.8 55 2 3
1.311 400 3 1
1.23 200 3 2
5.63 50 3 3

Answer 1

You'll get this error message if all values of a particular x variable are missing for a given time_id. Take a look at the example below where all values of x2 are missing for time_id 1, when you run the code the Results Output window details the problem (number of missing observations the same as the number of observations).
It works for firm_id because you have fewer values than time_id, therefore not all values of a particular x variable are missing for each firm_id.
data have;
input y x1 x2 firm_id time_id;
cards;
3.4 100 . 1 1
2.3 200 200 1 2
6.5 653 653 1 3
3 50 . 2 1
4.34 23 23 2 2
4.8 55 55 2 3
1.311 400 . 3 1
1.23 200 200 3 2
5.63 50 50 3 3
;
run;
proc sort data=have;
by time_id;
run;
ods output parameterestimates=pe;
proc reg data=have;
by time_id;
model y=x1-x2;
quit;
run;