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