Thanks Charles,
I'll have a look at the conditinoal logit function
One question: My strata is the "race" (Actually concatonation of date
and number) So the actual "values" used in the training set are
different than the test set. Will that matter? (In other words, when
training a clogit is the exact value of the strata saved as part of the
model, or is it just used for grouping?)
On 8/22/09 10:57 AM, Charles C. Berry wrote:
On Fri, 21 Aug 2009, Noah Silverman wrote:
Hi,
For fun, I'm trying to throw some horse racing data into either an
svm or lrm model. Curious to see what comes out as there are so many
published papers on this.
One thing I don't know how to do is to standardize the probabilities
by race.
This sounds closer to the conditional logit model.
However, if I recall correctly there is an assumption that in the
models of choice literature is stated something like 'independence of
alternatives that are unavailable'. That assumption might not hold in
a horse race where the speed at which a horse runs may depend on what
horses she is running against.
See
?survival:::clogit
and
@article{mcfadden1974conditional,
title={{Conditional logit analysis of qualitative choice behavior}},
author={McFadden, D.},
journal={Frontiers in econometrics},
volume={8},
pages={105--142},
year={1974}
}
BTW, Professor McFadden has a quintessentially American biography:
http://nobelprize.org/nobel_prizes/economics/laureates/2000/mcfadden-autobio.html
He mentions his personal background in farming and awards won for his
'sheep and geese', but alas does not mention horses or racing.
HTH,
Chuck
For example, if I train an LRM on a bunch of variable I get a model.
I can then get probability predictions from the model. That works.
It seems to me, that for a given race (8-12 horses) the probabilites
of my predictions should sum to one.
1) Is there some way to train the LRM to evaluate and then model the
subsequent date "per race"?? (Perhaps indicate some kind of grouping
variable?
2) Alternately, if I just run my data through a "standard" LRM, is
there some way to then "normalize" the probabilities in a correct way
for each upcoming race?
I've done some extensive research in this area and would be willing
to discuss more details offline with someone if they could contribute
to the process.
Thanks!!
-N
______________________________________________
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.
Charles C. Berry (858) 534-2098
Dept of Family/Preventive
Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego
92093-0901
______________________________________________
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.
