[R] using exists with coef from an arima fit

[Rolf Turner]

On 2/11/2009, at 5:27 PM, Erin Hodgess wrote:

> Dear R People:
>
> I have the output from an arima model fit in an object xxx.
>
> I want to verify that the ma1 coefficient is there, so I did the  
> following:
>> xxx$coef
>        ar1        ar2        ma1  intercept
>  1.3841297 -0.4985667 -0.9999996 -0.1091657
>> str(xxx$coef)
>  Named num [1:4] 1.384 -0.499 -1 -0.109
>  - attr(*, "names")= chr [1:4] "ar1" "ar2" "ma1" "intercept"
>> exists('xxx$coef["ma1"]')
> [1] FALSE
>>
>
> Other than using xxx$coef[3], is there another way to check this,  
> please?

(1) as.logical(length(grep("ma1",names(xxx$coef)))

(2) length(grep("ma1",names(xxx$coef))) != 0

(3) with(as.list(xxx$coef),exists("ma1"))

spring to mind.

	cheers,

		Rolf

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