[Rd] Error while fitting Partial Proportional Odds model using vglm
Rizwan Younis
rizwanyounis at hotmail.com
Mon Jul 16 23:27:28 CEST 2007
Dear R developers:
I am trying to fit a PPO model using vglm from the library VGAM, and get an
error while executing the code. Here is the data, code, and error:
Data: 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)
Ironically, it works ok with Proportional Odds (change parallel = T above),
but fails with PPO (parallel = F).
I will appreciate any help to fix this problem.
Thanks
Rizwan Younis
Grad Student
University of Waterloo
Waterloo, ON Canada
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