## Conditional Logistic Regression, Approximation Method

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# Conditional Logistic Regression, Approximation Method

Dear Community,

I am wondering if SAS has similar approximation procedure when fits the conditional logistic regression as R does?

I.e. In R, there is an option to specify likelihood approximation method as "efron" or "breslow".

I don't think PROC LOGISTIC has this option.

Thank you!

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Solution
‎01-18-2017 10:10 AM
Super Contributor
Posts: 301

## Re: Conditional Logistic Regression, Approximation Method

Posted in reply to JacobSimonsen
Sorry, I made a typing error. dummytime should be 1 for cases and 2 for controls (not 0). And the dummytime should be censored, so no riskset after 1:
model dummytime*dummytime(2)/ties=discrete

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Super User
Posts: 20,735

## Re: Conditional Logistic Regression, Approximation Method

Posted in reply to longitudinal

There are several proc that perform logistic regression, PROC GLM and PHREG are others.

This may be what you're looking for:
http://support.sas.com/documentation/cdl/en/statug/68162/HTML/default/viewer.htm#statug_phreg_exampl...

Super Contributor
Posts: 301

## Re: Conditional Logistic Regression, Approximation Method

It is true that proc logistic can not make the Breslow or Efron approximation. But, construction af variable "dummytime" with values 1 for cases and 0 for controls, and analyze this as survival analysis is equivalent to conditional logistic regression when using the option ties=discrete in PROC PHREG. If, instead, the option ties=breslow (default) or ties=efron is used, then you have the approximation.

Solution
‎01-18-2017 10:10 AM
Super Contributor
Posts: 301

## Re: Conditional Logistic Regression, Approximation Method

Posted in reply to JacobSimonsen
Sorry, I made a typing error. dummytime should be 1 for cases and 2 for controls (not 0). And the dummytime should be censored, so no riskset after 1:
model dummytime*dummytime(2)/ties=discrete
Occasional Contributor
Posts: 6

## Re: Conditional Logistic Regression, Approximation Method

Posted in reply to JacobSimonsen

I assume it should be the same as

model dummytime*Y(0)/ties=discrete

given that Y is binary with value 1 and 0?

Super Contributor
Posts: 301

## Re: Conditional Logistic Regression, Approximation Method

Posted in reply to longitudinal

Yes, that wil work also. If those with dummytime=2 is the same as those with Y=0, then

model dummytime*Y(0)/ties=discrete

is equivalent to

model dummytime*dummytime(2)/ties=discrete

given of course that the rest has dummytime=1.

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