[R] Manipulation of data.frame into an array

Thu May 24 17:47:25 CEST 2018

It would help if you show exactly the structure of your desired result, using the simple example data you supplied (what, exactly, do you mean by "array"?)

If you want mydata[[1]] "to provide the values for all three 3 variables (Y, X1 and X2) of the first imputation only" then this will do it:

> mydat <- list( Imputed[1:8,] , Imputed[9:16,] )
> mydat[[1]]
  X1 X2 Y
1  1  0 1
2  2  1 2
3  1  0 3
4  2  1 4
5  1  1 5
6  2  1 6
7  1  0 7
8  2  1 8

But mydata is not an array, it's a list.

The "[[ ]]" syntax doesn't particularly make sense on an array object:

> array(1:12, dim=c(2,3,2))
, , 1

     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

, , 2

     [,1] [,2] [,3]
[1,]    7    9   11
[2,]    8   10   12

> 
> array(1:12, dim=c(2,3,2))[[1]]
[1] 1

But "[[ ]]" does make sense on a list object.
--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062
Lab cell 925-724-7509

On 5/24/18, 8:14 AM, "R-help on behalf of Ioanna Ioannou" <r-help-bounces using r-project.org on behalf of ii54250 using msn.com> wrote:

    Hello everyone,

    Thank you for this. Nonetheless it is not exactly want i need.

    I need mydata[[1]] to provide the values for all 3 variables (Y, X1 and X2) of the first imputation only. As it stands it returns the whole database.

    Any ideas?

    Best,

    ioanna

    ________________________________
    From: Bert Gunter <bgunter.4567 using gmail.com>
    Sent: 24 May 2018 16:04
    To: Ioanna Ioannou
    Cc: r-help using r-project.org
    Subject: Re: [R] Manipulation of data.frame into an array

    This is one of those instances where a less superficial knowledge of R's technical details comes in really handy.

    What you need to do is convert the data frame to a single (numeric) vector for, e.g. a matrix() call. This can be easily done by noting that a data frame is also a list and using do.call():

    ## imp is the data frame:

    do.call(c,imp)

     X11  X12  X13  X14  X15  X16  X17  X18  X19 X110 X111 X112 X113 X114
       1    2    1    2    1    2    1    2    1    2    1    2    1    2
    X115 X116  X21  X22  X23  X24  X25  X26  X27  X28  X29 X210 X211 X212
       1    2    0    1    0    1    1    1    0    1    0    1    0    1
    X213 X214 X215 X216   Y1   Y2   Y3   Y4   Y5   Y6   Y7   Y8   Y9  Y10
       1    1    0    1    1    2    3    4    5    6    7    8    1    2
     Y11  Y12  Y13  Y14  Y15  Y16
       3    4    5    6    7    8

    So, e.g. for a 3 column matrix:

    > matrix(do.call(c,imp), ncol=3)
          [,1] [,2] [,3]
     [1,]    1    0    1
     [2,]    2    1    2
     [3,]    1    0    3
     [4,]    2    1    4
     [5,]    1    1    5
     [6,]    2    1    6
     [7,]    1    0    7
     [8,]    2    1    8
     [9,]    1    0    1
    [10,]    2    1    2
    [11,]    1    0    3
    [12,]    2    1    4
    [13,]    1    1    5
    [14,]    2    1    6
    [15,]    1    0    7
    [16,]    2    1    8

    Cheers,
    Bert

    Bert Gunter

    "The trouble with having an open mind is that people keep coming along and sticking things into it."
    -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

    On Thu, May 24, 2018 at 7:46 AM, Ioanna Ioannou <ii54250 using msn.com<mailto:ii54250 using msn.com>> wrote:
    Hello everyone,

     I want to transform a data.frame into an array (lets call it mydata), where: mydata[[1]] is the first imputed dataset...and for each mydata[[d]], the first p columns are covariates X, and the last one is the outcome Y.

    Lets assume a simple data.frame:

    Imputed = data.frame( X1 = c(1,2,1,2,1,2,1,2, 1,2,1,2,1,2,1,2),

                                              X2 = c(0,1,0,1,1,1,0,1, 0,1,0,1,1,1,0,1),

                                               Y   = c(1,2,3,4,5,6,7,8,1,2,3,4,5,6,7,8))

    The first 8 have been obtained by the first imputation and the later 8 by the 2nd.

    Can you help me please?

    Best,

    ioanna

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    ______________________________________________
    R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
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    PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
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