On Sun, 13 Mar 2011, Vlatka Matkovic Puljic wrote:
http://dl.dropbox.com/u/21595123/Book1.csv
Thanks. As I suspected. Due to the many 0.001 values, the starting value
selection does not work well. In the development version of betareg() I've
added a more useful warning message and an ad hoc workaround. Until it's
available, you need to select your own starting values (as suggested in my
previous e-mail).
For example:
## data
d <- read.csv2("Book1.csv")
## starting values
cf <- coef(lm(qlogis(cond) ~ alcoh + drug, data = d))
## basic regression model
m <- betareg(cond ~ alcoh + drug, data = d,
start = list(mean = cf, precision = 1))
## with precision regression
m2 <- betareg(cond ~ alcoh + drug | alcoh + drug, data = d,
start = list(mean = cf, precision = c(1, 0, 0)))
## estimate only a threshold model
m3 <- glm(factor(cond > 0.001) ~ alcoh + drug, data = d, family = binomial)
All three models show some positive but non-significant association
between the response and the regressors.
hth,
Z
2011/3/13 David Winsemius <dwinsem...@comcast.net>
Nothing came through. You need to read the posting guide.
On Mar 13, 2011, at 12:59 PM, Vlatka Matkovic Puljic wrote:
Sorry, here is my data (attached).
2011/3/12 Ben Bolker <bbol...@gmail.com>
Vlatka Matkovic Puljic <v.matkovic.puljic <at> gmail.com> writes:
That was also my first thought.
But I guess it has something to do with W and phihat
(which I'm struggling to check
Again, it would help to post a reproducible example ...
hard to debug/diagnose by remote control. If you can't
possibly post the data to the list, or put them on a web
site somewhere, or randomize them a bit so you're not
giving anything away, or find a simulated example that
shows the same problem, you could as a last resort send them
to me.
Ben Bolker
David Winsemius, MD
West Hartford, CT
--
**************************
Vlatka Matkovic Puljic
+32/ 485/ 453340
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