Ordered logit or probit

Has anyone written something that runs ordered logit or probit in R?  If
so, where might it be located...

Ordered logit models can be run using the polr() routine in the MASS
library.  Ordered probit requires a bit of source hacking; a cheesy,
undocumented retread of polr that does ordered probit instead is at
http://www.lordsutch.com/chris/oprobit.q; example use:

source("oprobit.q")
oprobit(as.ordered(impeach) ~ party + clinton_vote + marginality + ...)

In theory, ordered probit and ordered logit should give similar
results (although rescaled) for well-behaved data; however, if
something strange is going on in the tails (where the pdfs are
somewhat different), they can differ quite a bit.


Chris

Chris Lawrence <cnlawren at olemiss.edu> - http://www.lordsutch.com/chris/

Instructor and Ph.D. Candidate, Political Science, Univ. of Mississippi
208 Deupree Hall - 662-915-5765
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Dear R-users,

I'm trying to solve the following equation:

F=25*(F+0.2)/22.2/(EXP(F+0.2)-1)

In Excel I found F=0.696176718 but I'd like to know how to use R to solve
it. I tried, without success, to use "solve".

Thanks a lot,

Antonio Olinto






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You could try using 'uniroot':

f <- function(F) { F - (25*(F+0.2)/22.2/(exp(F+0.2)-1)) }
uniroot(f, c(0, 1))$root

[1] 0.6959678

-roger
_______________________________
UCLA Department of Statistics
rpeng at stat.ucla.edu
http://www.stat.ucla.edu/~rpeng

Dear R-users,

I'm trying to solve the following equation:

F=25*(F+0.2)/22.2/(EXP(F+0.2)-1)

In Excel I found F=0.696176718 but I'd like to know how to use R to solve
it. I tried, without success, to use "solve".

Thanks a lot,

Antonio Olinto






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r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

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r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

Dear R-users,

I'm trying to solve the following equation:

F=25*(F+0.2)/22.2/(EXP(F+0.2)-1)

In Excel I found F=0.696176718 but I'd like to know how to use R to solve
it. I tried, without success, to use "solve".

Use uniroot()

R> uniroot(function(F) F-25*(F+0.2)/22.2/(exp(F+0.2)-1), c(0,10))
$root
[1] 0.695973

$f.root
[1] -9.561183e-06

$iter
[1] 4

$estim.prec
[1] 6.103516e-05


	-thomas

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