topic Re: Number of subjects within each level of a specific CLASS variable from a mixed model (PROC MIXED in Statistical Procedures

Number of subjects within each level of a specific CLASS variable from a mixed model (PROC MIXED)

aaumez — Thu, 09 Nov 2017 20:14:14 GMT

Hi,

Does anyone know who to get the total number of subjects within each level of a specific CLASS variable from a mixed model (PROC MIXED)?

Note, this is not in reference to ods output=nobs or ods output=dim...but rather a more granular/extended version of ods output=dim that can actually provide how many unique subjects are in each group from a CLASS variable of interest.

Re: Number of subjects within each level of a specific CLASS variable from a mixed model (PROC MIXED

PaigeMiller — Thu, 09 Nov 2017 20:19:04 GMT

Maybe there's a way to do this in PROC MIXED, but the first thing that comes to mind is that PROC FREQ will provide the answer easily.

Re: Number of subjects within each level of a specific CLASS variable from a mixed model (PROC MIXED

aaumez — Fri, 10 Nov 2017 16:54:23 GMT

Agreed. SAS support confirmed there is no option for this.

Since I am only interested in the number of subjects with complete data (sufficient information) to predict Y at a given visit for each treatment group, I am using a simple descriptive frequency (proc sql and/or proc freq) of the count of unique subjects with non-missing data across all the variables included in the mixed model (excluding the outcome/dependent variable).

According to SAS:

"PROC MIXED does require non-missing values for the dependent variable for the model estimation. In other words, if an observation has a missing value for Y, it will not be included in the model estimation. However, you might obtain the predicted value for this observation, as long as all the independent variables in the model are non-missing. So you might want to modify how you count the subjects in your program, if the count is for the model estimation purpose."

Re: Number of subjects within each level of a specific CLASS variable from a mixed model (PROC MIXED

sld — Fri, 10 Nov 2017 05:35:59 GMT

This blog by Rick Wicklin ("Examine patterns of missing data in SAS") might be of interest to you

https://blogs.sas.com/content/iml/2016/04/18/patterns-of-missing-data-in-sas.html

Re: Number of subjects within each level of a specific CLASS variable from a mixed model (PROC MIXED

aaumez — Fri, 10 Nov 2017 12:59:55 GMT

Thank you for sharing. This will be a useful cross-check against proc sql and/or proc freq when getting the CLASS levels Ns.