[R] tibble question with a mean

[David L Carlson]

> xt[, 2:3] %>% colMeans
         y          z 
 2.5000000 -0.4401625

> xt[2] %>% colMeans
  y 
2.5 
> t(xt[, 2]) %>% mean
[1] 2.5

-------------------------
David L. Carlson
Department of Anthropology
Texas A&M University

-----Original Message-----
From: R-help [mailto:r-help-bounces using r-project.org] On Behalf Of Peter Langfelder
Sent: Thursday, September 20, 2018 8:08 PM
To: Erin Hodgess <erinm.hodgess using gmail.com>
Cc: r-help <r-help using r-project.org>
Subject: Re: [R] tibble question with a mean

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().

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