R help - Nov 2009 - using exists with coef from an arima fit

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


-- 
Erin Hodgess
Associate Professor
Department of Computer and Mathematical Sciences
University of Houston - Downtown
mailto: erinm.hodgess at gmail.com

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

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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