On Wed, Jun 25, 2008 at 6:00 PM, Victor Homar <victor.homar@uib.cat> wrote:

>
>   Hi, I'm trying to use sapply to compute the min of several variables,
> each
>   of them stored in data.frames, grouped as a list:
>   Is it normal that mean() and min() produce different objects dimensions?
>

it is exactly as documented in ?mean  and ?min

mean is a generic function which has a separate method for data frames:
mean.data.frame <- mean.data.frame
function (x, ...)  sapply(x, mean, ...)

min has no separate method for data frames (so you'll get just one number),
but you can define one easily:

min.data.frame <- function(...) sapply(..., min)


k

  > str(dats)
>   List of 5
>    $ log20:'data.frame':  83 obs. of  5 variables:
>      ..$  DATE  : int [1:83] 2001081500 2001081512 2001081600 2001081612
>   2001081700 2001081712 2001081800 2001081812 2001081900 2001081912 ...
>     ..$ logrho: num [1:83]  1.16 -1.30 -1.30 -1.30 -1.30 ...
>     ..$ w2    : num [1:83] 1.01 1.27 1.24 1.31 1.28 ...
>     ..$ rms   : num [1:83] 5.001 0.630 0.616 0.685 0.655 ...
>     ..$ maxi  : num [1:83] 8.66 3.39 3.83 3.35 3.23 ...
>    $ log30:'data.frame':  71 obs. of  5 variables:
>      ..$  DATE  : int [1:71] 2001081500 2001081512 2001081600 2001081612
>   2001081700 2001081712 2001081800 2001081812 2001081900 2001081912 ...
>     ..$ logrho: num [1:71]  1.16 -1.00 -1.00 -1.00 -1.00 ...
>     ..$ w2    : num [1:71] 1.01 1.27 1.21 1.29 1.27 ...
>     ..$ rms   : num [1:71] 5.001 0.851 0.802 0.877 0.864 ...
>     ..$ maxi  : num [1:71] 8.66 4.57 4.62 4.27 4.47 ...
>    $ log40:'data.frame':  14 obs. of  5 variables:
>      ..$  DATE  : int [1:14] 2001081500 2001081512 2001081600 2001081612
>   2001081700 2001081712 2001081800 2001081812 2001081900 2001081912 ...
>     ..$ logrho: num [1:14]  1.16 -0.50 -0.50 -0.50 -0.50 ...
>     ..$ w2    : num [1:14] 1.01 1.27 1.18 1.23 1.17 ...
>     ..$ rms   : num [1:14] 5.00 1.40 1.26 1.36 1.25 ...
>     ..$ maxi  : num [1:14] 8.66 7.54 6.39 6.68 5.83 ...
>    $ log50:'data.frame':  69 obs. of  5 variables:
>      ..$  DATE  : int [1:69] 2001081500 2001081512 2001081600 2001081612
>   2001081700 2001081712 2001081800 2001081812 2001081900 2001081912 ...
>     ..$ logrho: num [1:69]  1.16 -1.50 -1.50 -1.50 -1.50 ...
>     ..$ w2    : num [1:69] 1.01 1.27 1.25 1.33 1.31 ...
>     ..$ rms   : num [1:69] 5.001 0.516 0.516 0.577 0.554 ...
>     ..$ maxi  : num [1:69] 8.66 2.77 3.44 2.92 3.25 ...
>    $ log60:'data.frame':  66 obs. of  5 variables:
>      ..$  DATE  : int [1:66] 2001081500 2001081512 2001081600 2001081612
>   2001081700 2001081712 2001081800 2001081812 2001081900 2001081912 ...
>     ..$ logrho: num [1:66]  1.16 -2.00 -2.00 -2.00 -2.00 ...
>     ..$ w2    : num [1:66] 1.01 1.27 1.27 1.34 1.34 ...
>     ..$ rms   : num [1:66] 5.001 0.313 0.326 0.371 0.366 ...
>     ..$ maxi  : num [1:66] 8.66 1.68 2.43 2.23 3.85 ...
>   > sapply(dats,mean)
>                  log20         log30         log40         log50
> log60
>   DATE    2.001088e+09  2.001087e+09  2.001082e+09  2.001087e+09
>  2.001086e+09
>   logrho -1.270326e+00 -9.695748e-01 -3.816967e-01 -1.461383e+00
> -1.951941e+00
>   w2      1.324907e+00  1.283293e+00  1.217808e+00  1.345297e+00
>  1.398435e+00
>   rms     7.752963e-01  9.623266e-01  1.636949e+00  6.788993e-01
>  4.810029e-01
>   maxi    4.016900e+00  4.466865e+00  6.205573e+00  3.672405e+00
>  2.898055e+00
>   > sapply(dats,min)
>        log20      log30      log40      log50      log60
>   -1.3000708 -1.0000960 -0.5000176 -1.5001134 -2.0001350
>   Thanks for your help,
>   Víctor.
> --
> -----------------------------------------------------------------------
> Víctor Homar Santaner
> Grup de Meteorologia
>
> Edif. Mateu Orfila                      Tel: +34 971 17 1376
> Universitat de les Illes Balears        Fax: +34 971 17 3426
> 07122 Palma de Mallorca (SPAIN)         Email: [1]Victor.Homar@uib.es
>
>              Knowledge is contagious. Infect truth.
> -----------------------------------------------------------------------
>
> References
>
>   1. mailto:Victor.Homar@uib.es
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