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StrataVariables
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StrataVariables

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

Details

  • 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.

Examples

Basic Examples  (2)Summary of the most common use cases

Define some data:

In[1]:=1
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https://wolfram.com/xid/0gfokrwzwpme-i1novh

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

In[2]:=2
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https://wolfram.com/xid/0gfokrwzwpme-eo2qfz
Out[2]=2

One stratum is created for each level in the data:

In[3]:=3
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https://wolfram.com/xid/0gfokrwzwpme-c8m6vr
Out[3]=3

A parameter summary table:

In[4]:=4
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https://wolfram.com/xid/0gfokrwzwpme-jn6rqi
Out[4]=4

Fit a model with more than one strata variable:

In[1]:=1
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https://wolfram.com/xid/0gfokrwzwpme-lv57yc
In[2]:=2
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https://wolfram.com/xid/0gfokrwzwpme-gv2o34
Out[2]=2

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

In[3]:=3
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https://wolfram.com/xid/0gfokrwzwpme-bnoe1n
Out[3]=3

Baseline survival rates for the strata:

In[4]:=4
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https://wolfram.com/xid/0gfokrwzwpme-owrmz
Out[4]=4
Wolfram Research (2012), StrataVariables, Wolfram Language function, https://reference.wolfram.com/language/ref/StrataVariables.html.
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Wolfram Research (2012), StrataVariables, Wolfram Language function, https://reference.wolfram.com/language/ref/StrataVariables.html.

Text

Wolfram Research (2012), StrataVariables, Wolfram Language function, https://reference.wolfram.com/language/ref/StrataVariables.html.

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Wolfram Research (2012), StrataVariables, Wolfram Language function, https://reference.wolfram.com/language/ref/StrataVariables.html.

CMS

Wolfram Language. 2012. "StrataVariables." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/StrataVariables.html.

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Wolfram Language. 2012. "StrataVariables." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/StrataVariables.html.

APA

Wolfram Language. (2012). StrataVariables. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/StrataVariables.html

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Wolfram Language. (2012). StrataVariables. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/StrataVariables.html

BibTeX

@misc{reference.wolfram_2025_stratavariables, author="Wolfram Research", title="{StrataVariables}", year="2012", howpublished="\url{https://reference.wolfram.com/language/ref/StrataVariables.html}", note=[Accessed: 29-March-2025 ]}

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@misc{reference.wolfram_2025_stratavariables, author="Wolfram Research", title="{StrataVariables}", year="2012", howpublished="\url{https://reference.wolfram.com/language/ref/StrataVariables.html}", note=[Accessed: 29-March-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_stratavariables, organization={Wolfram Research}, title={StrataVariables}, year={2012}, url={https://reference.wolfram.com/language/ref/StrataVariables.html}, note=[Accessed: 29-March-2025 ]}

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@online{reference.wolfram_2025_stratavariables, organization={Wolfram Research}, title={StrataVariables}, year={2012}, url={https://reference.wolfram.com/language/ref/StrataVariables.html}, note=[Accessed: 29-March-2025 ]}