[R] Manipulation of data.frame into an array

[Ioanna Ioannou]

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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