[R] using exists with coef from an arima fit

[Peter Ehlers]

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?
> 
> Thanks in advance,
> Sincerely,
> Erin
> 
> 
co <- coef(xxx)["ma1"]
#or co <- coef(xxx)[["ma1"]] depending on whether you want to
# preserve the name

exists("co")
#[1] TRUE

  -Peter Ehlers