Proc glm looking for effect modification

[kristiepauly]

Hi All, 

I have a data set looking at diabetes and pulmonary function.  I want to see whether GOLD  (Global Initiative for Chronic Obstructive Lung Disease.) stage (with values from -1 to 4) modifies pulmonary function.  

I wrote this code to calculate the change in pulmonary function from the 3rd visit (..._P3) to the first visit (..._P1). 

data working4;
	set working3; 
	change_fev1 = fev1pp_Post_p3 - fev1pp_Post_p1;
	change_fev1_FVC = fev1_FVC_post_p3 - Fev1_FVC_post_p1;
	run;

Then I wrote this code to see if there was effect modification. 

Proc GLM data=working4; 
class finalgold_P3 (ref='GOLD 0');
model finalgold_p3 = finalgold_P3 change_fev1 change_fev1_FVC; *finalgold_p3*change_fev1 finalgold_p3*change_fev1_FVC;
lsmeans finalgold_P3 change_fev1 change_fev1_FVC finalgold_P3*change_fev1_FVC finalgold_P3*change_fev1/ pdiff;
format finalgold_p3 Final_GOLD_Stage.;
run;

But I get this error

 1          OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;
 68         
 69         Proc GLM data=working4;
 70         class finalgold_P3 (ref='GOLD 0');
 71         model finalgold_p3 = finalgold_P3 change_fev1 change_fev1_FVC; *finalgold_p3*change_fev1 finalgold_p3*change_fev1_FVC;
 72         lsmeans finalgold_P3 change_fev1 change_fev1_FVC finalgold_P3*change_fev1_FVC finalgold_P3*change_fev1/ pdiff;
 ERROR: Only CLASS variables allowed in this effect.
 NOTE: The previous statement has been deleted.
 73         format finalgold_p3 final_gold_stage.;
 74         run;
 
 75         
 76         OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;
 86  

I deleted finalgold_P3 from the right side of the equation but get this error: 

 1          OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;
 68         
 69         Proc glm data=working4;
 70         class finalgold_P3 (ref='GOLD 0');
 71         model finalgold_p3 = change_fev1 change_fev1_FVC;
 72         lsmeans finalgold_p3 change_fev1 change_fev1_FVC finalgold_P3*change_fev1_FVC finalgold_P3*change_fev1/pdiff;
 ERROR: Effects used in the LSMEANS statement must have appeared previously in the MODEL statement.
 NOTE: The previous statement has been deleted.
 73         format finalgold_P3 Final_GOLD_Stage.;
 74         run;
 
 75         
 76         OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;
 86  

I have finalgold_P3 formatted in previous code as follows. 

Proc Format;	
value Final_GOLD_Stage
	-1= "GOLD -1"				
	0 = "GOLD 0" 
	1 = "GOLD 1" 
	2 = "GOLD 2" 
	3 = "GOLD 3" 
	4 = "GOLD 4"
	other = Missing;
run;

Any suggestions are greatly appreciated. 

[PaigeMiller]

 72         lsmeans finalgold_P3 change_fev1 change_fev1_FVC finalgold_P3*change_fev1_FVC finalgold_P3*change_fev1/ pdiff;
 ERROR: Only CLASS variables allowed in this effect.
 NOTE: The previous statement has been deleted.

This seems pretty clear to me. Only CLASS variables can go in LSMEANS.

I deleted finalgold_P3 from the right side of the equation but get this error: 

Why would you delete finalgold_P3 from the model? it is a variable you are interested in.

 72         lsmeans finalgold_p3 change_fev1 change_fev1_FVC finalgold_P3*change_fev1_FVC finalgold_P3*change_fev1/pdiff;
 ERROR: Effects used in the LSMEANS statement must have appeared previously in the MODEL statement.
 NOTE: The previous statement has been deleted.

Seems pretty clear as well.