On Dec 4, 2009, at 5:49 PM, Hien Nguyen wrote:
Dear Dr. Winsemius,
Thank you very much for your reply.
I have tried many possible combinations (even with the model of only
2 predictors) but it produces the same message. With more than 4000
observations, I think 14 predictors might not be too many.
It is what happens in the factor combinations that concern me. I am
guessing that some of those predictors are factors. You really should
not ask r-help questions without providing better descriptions of both
the outcomes and the predictor variables.
Although my dependent variable (Pin) is not discrete (it ranges
from 0 to 1), I do not think it will create problems to the
estimation but I'm not sure
I would think it _would_ cause problems. As I understand it,
conditional methods create contingency tables. Why are you using an
outcome type that is not consistent with the fundamental regression
assumptions of the clogit function?
I do not get that particular error when I munge the infert dataset to
have case be a random uniform value, but I do get an error.
> infert$case <- runif(nrow(infert))
> clogit(case~spontaneous+induced+strata(stratum),data=infert)
Error in Surv(rep(1, 248L), case) : Invalid status value
So I certainly would not have proceeded to submit a full analysis to
clogit if I could not get a test case to run under the situation you
propose.
--
David
I have checked the collinearity among predictors and they are all <
0.5 (which I think is OK). Do you know what else could make this
errors?
Thanks a lot
Hien Nguyen
David Winsemius wrote:
On Dec 4, 2009, at 9:22 AM, Hien Nguyen wrote:
Dear R-helpers,
I am very new to R and trying to run the conditional logit model
using
"clogit " command.
I have more than 4000 observations in my dataset and try to
predict the
dependent variable from 14 independent variables. My command is as
follows
clmtest1 <-
clogit(Pin~Income+Bus+Pop+Urbpro+Health+Student+Grad+NE+NW+NCC+SCC
+CH+SE+MRD+strata(IDD),data=clmdata)
However, it produces the following errors:
Error in fitter(X, Y, strats, offset, init, control, weights =
weights, :
NA/NaN/Inf in foreign function call (arg 6)
In addition: Warning messages:
1: In Surv(rep(1, 4096L), Pinmig) : Invalid status value,
converted to NA
2: In fitter(X, Y, strats, offset, init, control, weights =
weights, :
Ran out of iterations and did not converge
I search the error message from R forums but it does not say
anything
for Conditional Logit Model.
With that many predictors in a small dataset, you may have created
matrix singularities. Perhaps you created a stratum where all of
the subjects experience the event and others where none did so. The
coefficients might be driven to infinities. Try simplifying the
model.
Please check for me what it says and what should I do to solve it.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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