[R] Partial Proportional Odds model using vglm

[Michael Dewey]

At 13:01 16/07/2007, Rizwan Younis wrote:
>Hi:
>I am trying to fit a PPO model using vglm from VGAM, and get an error while
>executing the code.

You seem to keep posting the same problem.
Since the only person who can tell you what is happening inside VGAM 
is probably the maintainer a more efficient strategy would be to 
email him as the instructions ask you to do.

However if that fails then try simplifying your problem to see if the 
error goes away
1) try merging ages 1 and 2, and ages 4 and 5
2) try merging column 3 "2" with 2 "1" or 4 "3"


>Here is the data, code, and error:
>
>Data  = rc13, first row is the column names. a = age, and 1,2,3, 4 and 5 are
>condition grades.
>
>   a  1 2 3  4 5
>   1  1 0 0  0 0
>   2 84 2 7 10 2
>   3 16 0 6  6 2
>   4 13 0 3  4 0
>   5  0 0 0  1 0
>
>Library(VGAM)
>
>rc13<-read.table("icg_rcPivot_group2.txt",header=F)
>names(rc13)<-c("a","1","2","3","4","5")
>
>ppo<-vglm(cbind(rc13[,2],rc13[,3],rc13[,4],rc13[,5],rc13[,6])~a,family =
>cumulative(link = logit, parallel = F , reverse = F),na.action=na.pass,
>data=rc13)
>summary(ppo)
>
>I get the following error:
>
>Error in "[<-"(`*tmp*`, , index, value = c(1.13512932539841,
>0.533057528200189,  :
>         number of items to replace is not a multiple of replacement length
>In addition: Warning messages:
>1: NaNs produced in: log(x)
>2: fitted values close to 0 or 1 in: tfun(mu = mu, y = y, w = w, res =
>FALSE, eta = eta, extra)
>3: 19 elements replaced by 1.819e-12 in: checkwz(wz, M = M, trace = trace,
>wzeps = control$wzepsilon)
>
>I will appreciate any help to fix this problem.
>Thanks
>
>Reez You
>Grad Student
>University of Waterloo
>Waterloo, ON Canada

Michael Dewey
http://www.aghmed.fsnet.co.uk