topic Re: Glimmix for categorical variable and repeated measures in SAS Procedures

Glimmix for categorical variable and repeated measures

soaresrd — Mon, 05 Oct 2015 20:41:38 GMT

Hi, I'm trying to assess the changes of my categorical data (MOV; with 5 ordinal scores) over time (day; 5 days) in 3 differents groups of animals (group). So, each animal whithin of each group was recorded by MOV score over 5 repeated days. I would like to know if the animals in each group has changed from score 1 to 5, for example over the days.

I know that is posible to to this using PROC GLIMMIX with day as random effect, but I don't know how. Does anybody know how to do this?

Re: Glimmix for categorical variable and repeated measures

PaigeMiller — Tue, 06 Oct 2015 12:40:19 GMT

@soaresrd wrote:
I would like to know if the animals in each group has changed from score 1 to 5, for example over the days.

Is this literally what you mean, did the score change from 1 to 5? Or do you mean did the mean score in each group change? Or do you mean something else?

Re: Glimmix for categorical variable and repeated measures

soaresrd — Tue, 06 Oct 2015 17:45:35 GMT

Hi, the variable MOV consisted of 5 scores (1: animal stood still for the entire assessment period; 2: animal stood still for most of the assessment period; 3: animal reacted calmly at least half of the assessment period; 4: animal reacted intensely more than half of the assessment period; 5: the animal jumped, raised its limbs off the ground). So, I would like to see if the animals changed their scores over time (day 1, day 2, day3, day 4, and day5) by each breed (breed 1, 2 and 3).

My appologizes for my poor English.

Re: Glimmix for categorical variable and repeated measures

PaigeMiller — Tue, 06 Oct 2015 19:50:41 GMT

My answer is: I don't know what the best analysis is.

PROC GLIMMIX does not have a REPEATED statement, so you could include the days into the model as an ordinary (not repeated measure) factor.

PROC GLM has a REPEATED statement, and so you could consider the response to be continuous and use PROC GLM.

PROC CATMOD has a REPEATED statement, and allows you to handle your response as ordinal rather than continuous; this seems to come the closest to giving you the proper analysis, but I guess I'd need to think about using this some more.

Re: Glimmix for categorical variable and repeated measures

soaresrd — Tue, 06 Oct 2015 20:56:03 GMT

Thank you for your answer, but I think that is not apropriate consider MOV score as continuous data. The distribution is not even close of normal distribution.I saw on this book (Generalized Linear Mixed Models, Walter W. Stroup, 2012) that I can use proc glimmix with multinomial distribution, but I don't know yet how to do the model. I saw that could be something like this:

proc glimmix data=mydata;

class animal breed day;

model mov (order=data) = breed day breed*day / dist=multinomial solution oddsratio;

random intercept / subject = animal;

freq mov;

run;

But I am not so sure if is right and I know that I missed something in this model.