Proc GLM looking at effect modification

[kristiepauly]

Hi All, 

My data set is looking at diabetes and pulmonary function over time.  I need to determine whether the GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage (-1 - 4) modifies the effect of pulmonary function.  

I added this code to calculate the change in pulmonary function at visit 3 (....._p3) minus the baseline 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;

I then used proc glm to try to determine EM. 

Proc GLM data=working4; 
	class finalgold_P3 (ref='GOLD 0');
	model finalgold_p3 = change_fev1 change_fev1_FVC; ***I don't think I need this code....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;

and get this error message: 

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 finalgold_P3; * i don't think i need this here..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;

If I use the same code but delete "finalgold_P3" from the right side of the = sign in the model statement, I get this error message: 

 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;
 
 75         
 76         OPTIONS NONOTES NOSTIMER NOSOURCE NOSYNTAXCHECK;

Any suggestions are greatly appreciated. 

[PaigeMiller]

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