[R] S4 object slot of type 'call'

[Roberto Brunelli]

I'm using an S4 object with a slot of type 'call': I would like to be able to initialize 
it with something like NULL or NA (indicating that there is no information in the slot)
but the value should comply with the fact that it must be of type call.

Is there any simple way to obtain this?

Thanks for any hint,

	Roberto

-- 
	<r/>
| Roberto Brunelli - [scientist at  Fondazione Bruno Kessler-irst]
|           'Home can be anywhere, for it is a part of one's self'

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ITC -> dall'1 marzo 2007 Fondazione Bruno Kessler
ITC -> since 1 March 2007 Fondazione Bruno Kessler