[R] [FORGED] Re: tibble question with a mean

[Erin Hodgess]

Thanks to all for the good suggestions!!!

Erin Hodgess, PhD
mailto: erinm.hodgess using gmail.com


On Thu, Sep 20, 2018 at 7:38 PM Rolf Turner <r.turner using auckland.ac.nz> wrote:

>
> Please see inline below.
>
> n 09/21/2018 01:07 PM, Peter Langfelder wrote:
> > I don't know tibble, so I'll do the same with a plain data frame:
> >
> > a =
> >
> data.frame(x=LETTERS[1:4],y=1:4,z=rnorm(4),a=c("dog","cat","tree","ferret"))
> >> a
> >    x y           z      a
> > 1 A 1 -0.08264865    dog
> > 2 B 2  0.32344426    cat
> > 3 C 3 -0.80416061   tree
> > 4 D 4  1.27052529 ferret
> >> mean(a[2:3])
> > [1] NA
> > Warning message:
> > In mean.default(a[2:3]) : argument is not numeric or logical: returning
> NA
> >> mean(as.matrix(a[2:3]))
> > [1] 1.338395
> >
> > The reason you get an error on mean(a[2:3]) is that a[2:3] is still a
> data
> > frame (a special list) and you cannot simply apply mean to a list. You
> need
> > to first convert to a matrix or vector which can then be fed to mean().
>
> Perhaps
>
> sapply(a[2:3],mean)?
>
> cheers,
>
> Rolf
>
> >
> > Peter
> >
> >
> > On Thu, Sep 20, 2018 at 5:50 PM Erin Hodgess <erinm.hodgess using gmail.com>
> > wrote:
> >
> >> Hello!
> >>
> >> Here is a toy tibble problem:
> >>
> >> xt <-
> >> tibble(x=LETTERS[1:4],y=1:4,z=rnorm(4),a=c("dog","cat","tree","ferret"))
> >> str(xt)
> >> Classes ‘tbl_df’, ‘tbl’ and 'data.frame': 4 obs. of  4 variables:
> >>   $ x: chr  "A" "B" "C" "D"
> >>   $ y: int  1 2 3 4
> >>   $ z: num  0.3246 0.0504 0.339 0.4872
> >>   $ a: chr  "dog" "cat" "tree" "ferret"
> >> #No surprise
> >>   xt %>% mean
> >> [1] NA
> >> Warning message:
> >> In mean.default(.) : argument is not numeric or logical: returning NA
> >> #surprised!
> >> mean(xt[2:3])
> >> [1] NA
> >> Warning message:
> >> In mean.default(xt[2:3]) : argument is not numeric or logical:
> returning NA
> >>   xt[, 2:3] %>% mean
> >> [1] NA
> >> Warning message:
> >> In mean.default(.) : argument is not numeric or logical: returning NA
> >>
> >> I have a feeling that I'm doing something silly wrong.  Has anyone run
> into
> >> this, please?  I saw something like this on this list, but didn't see a
> >> solution.
> >>
> >> Thanks,
> >> Erin
>

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