[Rd] Bug in package stats function ar() (PR#10459)

[Ben Bolker]

Steven McKinney wrote:
> 
> Full_Name: Steven McKinney
> Version: 2.6.0
> OS: OS X
> Submission from: (NULL) (142.103.207.10)
> 
> 
> 
> Function ar() in package "stats" is showing
> a quirky bug.  Some calls to ar() run to
> completion, others throw an error.
> 
> The bug is reproducible by several people on different
> machines, however, the ar() function itself ends
> up throwing the error sporadically.  Several calls to
> ar() may be necessary to trip the error condition.
> 
> Code to reproduce:
> 
> x<-ts(c(-0.2052083,-0.3764986,-0.3762448,0.3740089,0.2737568,2.8235722,-1.7783313,0.2728676,-0.3273164),start=c(1978,3),frequency=4,end=c(1980,3))
> # ar function
> res.ar<-ar(x,aic=TRUE,demean=F)
> # call "ar" again and ............
> res.ar<-ar(x,aic=TRUE,demean=F)
> 
> 
> Example output:
> (Note that on this attempt the first call to ar()
>  tripped the error.)
> 
>> x<-ts(c(-0.2052083,-0.3764986,-0.3762448,0.3740089,0.2737568,2.8235722,-
> +
> 1.7783313,0.2728676,-0.3273164),start=c(1978,3),frequency=4,end=c(1980,3))
>> 
> 

 Slightly more detail: in the "eureka" function, in stats/src/eureka.f, the
last
element of "vars" in the return list is bogus and varies among calls; if it
comes out to NaN or NA it triggers the bug.

  Haven't spent any more time yet tracking this down, but hope that
will save someone a few minutes.

   Ben Bolker
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