[R] GLM fitting

[Charles Annis, P.E.]

Vito:

Please plot your data:

y <- c(1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0)
x <- c(37, 35, 33, 40, 45, 41, 42, 20, 21, 25, 27, 29, 18)
plot(x, y)

You will see that ANY step function between 29 < x < 33 will describe these
observations perfectly.


Charles Annis, P.E.
 
Charles.Annis at StatisticalEngineering.com
phone: 561-352-9699
eFax:  614-455-3265
http://www.StatisticalEngineering.com

-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Vito Ricci
Sent: Friday, January 28, 2005 5:14 AM
To: r-help at stat.math.ethz.ch
Subject: [R] GLM fitting

DeaR R-useRs,

I'm trying to fit a logist model with these data:

> dati
   y  x
1  1 37
2  1 35
3  1 33
4  1 40
5  1 45
6  1 41
7  1 42
8  0 20
9  0 21
10 0 25
11 0 27
12 0 29
13 0 18

I use glm(), having this output:

> g<-glm(y~x,family=binomial,data=dati)
Warning messages: 
1: Algorithm did not converge in: glm.fit(x = X, y =
Y, weights = weights, start = start, etastart =
etastart,  
2: fitted probabilities numerically 0 or 1 occurred
in: glm.fit(x = X, y = Y, weights = weights, start =
start, etastart = etastart,  
> g

Call:  glm(formula = y ~ x, family = binomial, data =
dati) 

Coefficients:
(Intercept)            x  
    -348.23        11.23  

Degrees of Freedom: 12 Total (i.e. Null);  11 Residual
Null Deviance:      17.94 
Residual Deviance: 7.011e-10    AIC: 4 

I don't understand the meaning of warning. Can anyone
help me? Many thanks.
Cheers,
Vito


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