R - cox hazard model not including levels of a factor
问题 I am fitting a cox model to some data that is structured as such: str(test) 'data.frame': 147 obs. of 8 variables: $ AGE : int 71 69 90 78 61 74 78 78 81 45 ... $ Gender : Factor w/ 2 levels "F","M": 2 1 2 1 2 1 2 1 2 1 ... $ RACE : Factor w/ 5 levels "","BLACK","HISPANIC",..: 5 2 5 5 5 5 5 5 5 1 ... $ SIDE : Factor w/ 2 levels "L","R": 1 1 2 1 2 1 1 1 2 1 ... $ LESION.INDICATION: Factor w/ 12 levels "CLAUDICATION",..: 1 11 4 11 9 1 1 11 11 11 ... $ RUTH.CLASS : int 3 5 4 5 4 3 3 5 5 5 ... $