Carbajal, Armida J wrote:
Prof. Harrell,
My name is Armida Carbajal, I'm a graduate student intern at Sandia National
Laboratories (SNL) and am conducting some research for my thesis project at the
University of New Mexico in Statistics for SNL.
My project entails a logistic regression and I wanted to create a
classification table like the one found in SAS using the function CTABLE. I was
running out of ideas on creating code, as I am far from proficient in R. I did
a google search and found this comment.
I understand the probabilities are highly arbitrary but I thought this would be
useful. You see, I am studying a variable that is not understood in our
process. I have derived a logistic regression and well I wanted to determine
how specific and how sensitive the model was. I really didn't plan on selecting
a cutoff point. I was just going to use this piece of statistical information
to give the engineers interested in this information an idea of the sensitivity
vs. specificity of the model so that they could decide what actions to take
based on what probabilities.
I am just very curious in getting your opinion in a situation like this. Your
response would be highly appreciated.
Regards,
Armida J. Carbajal
Graduate Student Intern
Sandia National Laboratories
Dept of Analytical Technologies
ajca...@sandia.gov
ajca...@gmail.com
505-284-9854 (office)
Armida,
I regret putting CTABLE as an option on the old SAS PROC LOGIS which was
a basis for PROC LOGISTIC. Classification tables are arbitrary and
misleading so I would stay away from them.
You might build a model with and without the variable of interest and
plot the two predicted probabilities against each other for more insight
than what is provided by a classification table.
Frank
--
Frank E Harrell Jr Professor and Chair School of Medicine
Department of Biostatistics Vanderbilt University
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
