"when the first level denotes failure and all others success"
Yes, I saw this sentence in the glm help file, but I hadn't understood it
this way... Anyway I checked this with a few examples and this is exactly
what it does.
Thanks a lot for your help !!!
I can go back now to the polr function and try to understand why my results
were better with glm.
By the way, does anyone know how I can solve the likelyhood maximization
problem :
"attempt to find suitable starting values failed"
obtained with polr :
require(MASS)
data(iris)
polr(Species~Sepal.Length+Sepal.Width+Petal.Length+Petal.Width,iris)
(I know this has to be a nominal model but I do as levels were ordered for
the example).
I tried to solve this by setting the "start" option to a null or a random
vector by it doesn't garantee to find "a good" solution at the end.
Thanks a lot !