StrataVariables

StrataVariables
is an option for fitting functions such as CoxModelFit that specify the variables on which the model should be stratified.

DetailsDetails

  • Strata variables are used to divide a non-homogeneous population into homogeneous subgroups. Stratification is often useful in proportional hazards modeling where the assumption of proportional hazards between subgroups may be suspect.
  • Possible settings for StrataVariables include:
  • Nonetreat no variables as strata
    {v1,v2,}treat the variables vi as strata
  • Models with a strata variable v with p levels {s1,,sp} effectively group the input data into p groups corresponding to the si.
  • With multiple strata variables v1, , vk with pvi levels, the input data is grouped into at most pvi groups, dropping empty subgroups.

ExamplesExamplesopen allclose all

Basic Examples  (2)Basic Examples  (2)

Define some data:

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Fit the data, treating the second variable as a strata variable:

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One stratum is created for each level in the data:

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A parameter summary table:

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Fit a model with more than one strata variable:

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All non-empty combinations of the strata variables are used:

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Baseline survival rates for the strata:

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Introduced in 2012
(9.0)
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