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  • modeling logit(y/n) using lrm

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    I have a dataset at a hospital level (as opposed to the patient level)
    that contains number of patients experiencing events (call this number
    y), and the number of patients eligible for such events (call this
    number n). I am trying to model logit(y/n) = XBeta. In SAS this can be
    done in PRC LGISTIC or GENMD with a model statement such as: model
    y/n = <predictors>;. Can this be done using lrm from the Hmisc library
    without restructuring the dataset so that for each hospital there is one
    row with y = 1 and one row with y = 0 and then using the weight option
    in lrm to weight these two responses by the number of 'successes' and
    'failures' for that hospital, respectively? I would like to avoid the
    restructuring, and I understand that the use of the weight function is
    not compatible with a lot of the validation functions available in Hmisc
    (validate, bootcov, etc.).
    Cody Hamilton, Ph.D
    Institute for Health Care Research and Improvement
    Baylor Health Care System
    (214) 265-3618
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  • No.1 | | 1277 bytes | |

    Hamilton, Cody wrote:
    I have a dataset at a hospital level (as opposed to the patient level)
    that contains number of patients experiencing events (call this number
    y), and the number of patients eligible for such events (call this
    number n). I am trying to model logit(y/n) = XBeta. In SAS this can be
    done in PRC LGISTIC or GENMD with a model statement such as: model
    y/n = <predictors>;. Can this be done using lrm from the Hmisc library
    without restructuring the dataset so that for each hospital there is one
    row with y = 1 and one row with y = 0 and then using the weight option
    in lrm to weight these two responses by the number of 'successes' and
    'failures' for that hospital, respectively? I would like to avoid the
    restructuring, and I understand that the use of the weight function is
    not compatible with a lot of the validation functions available in Hmisc
    (validate, bootcov, etc.).

    I don't know about lrm, but for glm you can do
    glm(cbind(y,m)~ ) where y is number of successes and
    m is the number of failures.

    So, you might try that.

    Cody Hamilton, Ph.D

    Institute for Health Care Research and Improvement

    Baylor Health Care System

    (214) 265-3618
  • No.2 | | 1462 bytes | |

    "Kevin E. Thorpe" <kevin.thorpe (AT) utoronto (DOT) cawrites:

    Hamilton, Cody wrote:
    I have a dataset at a hospital level (as opposed to the patient level)
    that contains number of patients experiencing events (call this number
    y), and the number of patients eligible for such events (call this
    number n). I am trying to model logit(y/n) = XBeta. In SAS this can be
    done in PRC LGISTIC or GENMD with a model statement such as: model
    y/n = <predictors>;. Can this be done using lrm from the Hmisc library
    without restructuring the dataset so that for each hospital there is one
    row with y = 1 and one row with y = 0 and then using the weight option
    in lrm to weight these two responses by the number of 'successes' and
    'failures' for that hospital, respectively? I would like to avoid the
    restructuring, and I understand that the use of the weight function is
    not compatible with a lot of the validation functions available in Hmisc
    (validate, bootcov, etc.).

    I don't know about lrm, but for glm you can do
    glm(cbind(y,m)~ ) where y is number of successes and
    m is the number of failures.

    glm(y/n~, binomial, weight=n)

    should work as well. I suspect that this passes trough to lrm, too.

    So, you might try that.

    Cody Hamilton, Ph.D

    Institute for Health Care Research and Improvement

    Baylor Health Care System

    (214) 265-3618

Re: modeling logit(y/n) using lrm


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