Variable List Subcommand (CSCOXREG command)

The variable list specifies the time variables, the factors, and the covariates in the model.

  • The time variables starttime (if specified) and endtime must be listed first. These variables represent the endpoints of a time interval (starttime, endtime) during which the case is at risk.
  • When starttime is not specified, it is implied that starttime = 0 for all cases if an ID variable is not specified. If an ID variable is specified, it is assumed that starttime = 0 for the first observation for that subject and starttime for following observations equals endtime of the previous observation. See the example below.
  • The time variables must be numeric and non-negative.
  • If the time variables are of Date or Time type, the internal numeric representation will be used and a warning will be given. For example, November 8, 1957, is 1.2E+10 (the number of seconds from midnight, October 14, 1582). See Date and time functions for detailed internal numeric representation of different date and time formats.
  • The names of the factors and covariates, if any, follow the time variables. Specify any factors following the keyword BY. Specify any covariates following the keyword WITH.
  • Factors can be numeric or string variables, but covariates must be numeric.
  • Each variable may be specified only once on the variable list.
  • The status variable, ID variable, baseline strata variable, and subpopulation variables may not be specified on the variable list.

Example

CSCOXREG tstart tend BY a b c WITH x
  /VARIABLES STATUS = dead(1) ID = SSN
  /PLAN FILE=’c:\survey\myfile.csplan’
  /MODEL a b c a*b a*c b*c x.
  • Two time variables, tstart and tend, are specified.
  • ID specifies SSN as the subject ID variable. All cases sharing the same value of SSN belong to the same subject.
  • This example fits a model that includes the main effects for factors a, b, and c; all two-way interactions among the factors; and the covariate x. 
    CSCOXREG tend BY a b c WITH x
  /VARIABLES STATUS = dead(1) ID = SSN
  /PLAN FILE=’c:\survey\myfile.csplan’
  /MODEL a b c a*b a*c b*c x.
  • This is the same as the above example except that only one time variable, tend, is specified.