[R] Re strict AIC comparison to succesful models?

[Ben Bolker]

Manuel Morales wrote:
> On Thu, 2009-06-11 at 12:08 -0700, Ben Bolker wrote:
>>
>> Manuel Morales wrote:
>>> Hello list,
>>>
>>> I'm doing a bootstrap analysis where some models occasionally fail to
>>> converge. I'd like to automate the process of restricting AIC to the
>>> models that do converge. A contrived example of what I'd like to do is
>>> below:
>>>
>>> resp <- c(1,1,2)
>>> pred <- c(1,2,3)
>>>
>>> m1 <- lm(resp~pred)
>>> m2 <- lm(resp~poly(pred,2))
>>> m3 <- lm(resp~poly(pred,3)) # Fails, obviously
>>>
>>> ## Some test to see which models were successful
>>> models <- test(m1,m2,m3)
>>>
>>     How about 
>>
>> models <- list(m1,m2,m3)
>> is.OK <- sapply(models,test)
>> do.call(AIC,models[is.OK])
>>
>>   ?
> 
> Good idea but unfortunately I get an error message with:
> 
> models <- list(m1,m2,m3)
> test <- function(x) length(x)>1
> is.OK <- sapply(models,test)
> do.call(AIC,models[is.OK])
> 
> I think the issue is that AIC is expecting a ... of model objects (not a
> list or a vector) and I'm not sure how to construct that.
> 
> Manuel
> 

  The problem is that when your fitting function fails,
NOTHING gets created.

   Try this:

#####################
resp <- c(1,1,2)
pred <- c(1,2,3)

m1 <- try(lm(resp~pred))
m2 <- try(lm(resp~poly(pred,2)))
m3 <- try(lm(resp~poly(pred,3))) # Fails, obviously

models <- list(m1,m2,m3)
test <- function(x) !inherits(x,"try-error")
is.OK <- sapply(models,test)

AIC(m1,m2) ## works

## all these work but lead to objects with ugly row names
do.call(AIC,models[is.OK])
do.call("AIC",models[is.OK])
do.call(stats:::AIC.default,models[is.OK])
dd <- do.call(AIC,list(m1,m2))
rownames(dd) <- NULL
dd


-- 
Ben Bolker
Associate professor, Biology Dep't, Univ. of Florida
bolker at ufl.edu / www.zoology.ufl.edu/bolker
GPG key: www.zoology.ufl.edu/bolker/benbolker-publickey.asc

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