[R] (no subject)

[FERNANDO MANSITO CABALLERO]

Hi

Thanks a lot to all of you for your solutions and explanations.

On Sun, Oct 4, 2015 at 10:34 PM, David Winsemius <dwinsemius at comcast.net>
wrote:

>
> On Oct 4, 2015, at 11:31 AM, FERNANDO MANSITO CABALLERO wrote:
>
> > Dear Madam/Sir,
> >
> > I  am   trying to understand  R and I have come to a stumbling block. i
> > have written:
> >
> >> Empl <- list(employee="Anna",family=list(spouse="Fred",children=3,
> >
> +child.ages=c(4,7,9)),employee="John",family=list(spouse="Mary",children=2,
> > +child.ages=c(14,17)))
> >> $family$spouse
> > [1] "Fred"
> >> #instead of [1] "Fred" "Mary"
> >
> > Where am I wrong?
>
> The $ function is short-hand for "[[" (with an unevaluated argument). The
> "[[" function is not able to deliver multiple values. You might think you
> needed to use:
>
> sapply( Empl[c(2,4)], function(x){ x$family$spouse )
>
>
> And you cannot use that construction or its equivalent, because sapply and
> lapply do not pass the names of their arguments:
>
> > sapply( Empl[c(2,4)], function(x){ x[['family']]['spouse']} )
> $family
> NULL
>
> $family
> NULL
>
> #-----------
>
>
> This succeeds:
>
> > sapply( Empl[grepl('family', names(Empl)) ], function(x){x$spouse})
> family family
> "Fred" "Mary"
>
>
> --
>
> David Winsemius
> Alameda, CA, USA
>
>

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