topic Re: Trouble with BY-group processing using GLM parameterization in Statistical Procedures

Trouble with BY-group processing using GLM parameterization

EastwoodDC42 — Wed, 12 Feb 2025 22:04:25 GMT

Greetings SASsers,

I am setting up a bootstrap analysis of a multinomial model in Proc Logistic and getting this warning:
WARNING: The current by-group is not processed because the ordering of the levels of Smoker_NXT are different from their ordering across all by-groups.
which is unexpected because my data is sorted. My log file, lightly edited for brevity:

NOTE: Copyright (c) 2016 by SAS Institute Inc., Cary, NC, USA. 
NOTE: SAS (r) Proprietary Software 9.4 (TS1M7) 
Licensed to UNIVERSITY OF NEW MEXICO - ADMIN, Site 70080754.
NOTE: This session is executing on the X64_10PRO platform.

2791       proc sort data=boots2;  by Replicate Smoker_NXT   ; 
2793       run;

NOTE: There were 243174 observations read from the data set WORK.BOOTS2.

2808       proc logistic data=boots2 order=formatted plots=none ;
2809       by Replicate;
2813       	class   Wave(ref='1')  AgeStartCIGS(ref='18-24')
2813     ! Age1stIview(ref='18-24') Sex(ref='Male')
2814       		Race(ref='White alone') Hispanic(ref='Non-Hispanic')
2815       		Smoker(ref='No') Smoker_NXT(ref='No') ENDSer(ref='No')
2816       		Start2SMK(ref='No')  SmkHistory(ref=first)  /  param=glm;
2817       
2818       	model Smoker_NXT =  AgeStartCIGS  Age1stIview Sex  Race  Hispanic	Wave|Smoker|ENDSer   SmkHistory   Start2SMK  /  noint
2819     ! link=glogit  Singular=1E-7  ;
2820       	weight tWGT ;
2829       run;

WARNING: The current by-group is not processed because the ordering of the 
         levels of Smoker_NXT are different from their ordering across all 
         by-groups.
NOTE: The above message was for the following BY group:
      Sample Replicate Number=1
NOTE: There were 243174 observations read from the data set WORK.BOOTS2.
NOTE: PROCEDURE LOGISTIC used (Total process time):

I get this warning for all By-Replicate groups, even for only a single group, but not if I remove the "BY Replicate;" statement.

My code:

proc sort data=boots2;  
by Replicate Smoker_NXT   ; 
run;

proc logistic data=boots2 order=data plots=none ;
by Replicate;
class   Wave(ref='1')  AgeStartCIGS(ref='18-24') Age1stIview(ref='18-24') Sex(ref='Male')  Race(ref='White alone') Hispanic(ref='Non-Hispanic') Smoker(ref='No') Smoker_NXT(ref='No') ENDSer(ref='No') 		Start2SMK(ref='No')  SmkHistory(ref=first)  /  param=glm;
model Smoker_NXT = AgeStartCIGS Age1stIview Sex Race Hispanic Wave|Smoker|ENDSer SmkHistory Start2SMK  /  noint link=glogit  Singular=1E-7  ;
weight tWGT ;
run;

Note1: "order=data" was suggested in one of the warning message, but it doesn't resolve the warning.
Note2: The warning goes away if I switch from Param=GLM to Param=REF, but I am hoping to use LSMEANS to get the interaction results.

TIA!

Re: Trouble with BY-group processing using GLM parameterization

Tom — Wed, 12 Feb 2025 23:11:32 GMT

Does every value of Replicate have the same set of values of Smoker_NXT?

Do any of the other analysis variables have missing values? PROC LOGISTIC should eliminate those observations. Could that cause one of the values of Smoker_NXT to drop out for a group?

Re: Trouble with BY-group processing using GLM parameterization

Ksharp — Thu, 13 Feb 2025 02:09:22 GMT

Firstly, make sure in each of Replicate, you have both No and Yes.

a.k.a you have right data structure to build a LOGISTIC Model.

Use this code to check:

proc freq data=boots2 ;
table Replicate*Smoker_NXT /list;
run;

I think your code should like:

class   Wave(ref='1')  AgeStartCIGS(ref='18-24') Age1stIview(ref='18-24') Sex(ref='Male')  
Race(ref='White alone') Hispanic(ref='Non-Hispanic') Smoker(ref='No') Smoker_NXT(ref='No') 
ENDSer(ref='No') 		Start2SMK(ref='No')  SmkHistory(ref=first)  /  param=glm;
model Smoker_NXT = AgeStartCIGS Age1stIview Sex Race Hispanic Wave|Smoker|ENDSer SmkHistory 
Start2SMK  /  noint link=glogit  Singular=1E-7  ;

----->

class   Wave(ref='1')  AgeStartCIGS(ref='18-24') Age1stIview(ref='18-24') Sex(ref='Male') 
Race(ref='White alone') Hispanic(ref='Non-Hispanic') Smoker(ref='No')  
ENDSer(ref='No') 		Start2SMK(ref='No')  SmkHistory(ref=first)  /  param=glm;
model Smoker_NXT(ref='No') = AgeStartCIGS Age1stIview Sex Race Hispanic Wave|Smoker|ENDSer SmkHistory
Start2SMK  /  noint link=glogit  Singular=1E-7  ;

NOTE: there is not Smoker_NXT in CLASS statement.

If that still does not work, try using another level of Smoker_NXT( ref='Yes'):

class   Wave(ref='1')  AgeStartCIGS(ref='18-24') Age1stIview(ref='18-24') Sex(ref='Male') 
Race(ref='White alone') Hispanic(ref='Non-Hispanic') Smoker(ref='No')  
ENDSer(ref='No') 		Start2SMK(ref='No')  SmkHistory(ref=first)  /  param=glm;
model Smoker_NXT(ref='Yes') = AgeStartCIGS Age1stIview Sex Race Hispanic Wave|Smoker|ENDSer SmkHistory
Start2SMK  /  noint link=glogit  Singular=1E-7

Re: Trouble with BY-group processing using GLM parameterization

EastwoodDC42 — Thu, 13 Feb 2025 17:39:14 GMT

@Tom
Does every value of Replicate have the same set of values of Smoker_NXT?

They do. I suspect some interaction between the glogit link and by-processing.

Each subject might be surveyed up to 7 times, and the third level of response is "No Response" to the survey. On consideration I can drop the non-response and simplify to a logistic regression.

Thanks for your time!

Re: Trouble with BY-group processing using GLM parameterization

EastwoodDC42 — Thu, 13 Feb 2025 17:44:25 GMT

@Ksharp
You suggestion of removing Smoker_NXT from the CLASS statement appears to have resolved the level-ordering problem (Hurray!), but now I have convergence issues. As I noted to @Tom above, I can simplify the model, which might solve the convergence problems too.

Thanks again for your time!

Dan