Categorical time dependent covariate in Cox

[haoduonge]

Hi all,

I found this topic was discussed before. I figured out how to use it for dichotomous or continuous variable, but I don't find any example in which time dependent covariate is categorical (0, 1,2,3).

Please share if you have coding example modeling categorical time dependent variable/covariate.

Thank you!

Hao

https://support.sas.com/documentation/cdl/en/statug/63347/HTML/default/viewer.htm#statug_phreg_sect0... 

[PhilC]

Categorical and ordinal variables should be converted to dichotomous variables.   Why.  There are more intricate explanations, so long story short:  Grade level, e.g. in the US: K, 1 through 12,  is an ordinal variable.  It can't be used as a analysis variables because there is no sense in taking the difference in grade nor the mean of grade.  K, 1 through 12 are categories, they would work equally well if they were labeled A,B..M.  being ordinal, there is only the set mathematical relationships that begin  grade K is less than grade 1 through 12, 1 less than grade 2, etc.

Look at page 13 of this pdf to see how Gender can be coded with a dichotomous variable scheme.  Mind you this is not the only way to do it.

referring to:  SD-29.pdf (lexjansen.com)

[haoduonge]

Thanks!