[R] converting each column of a data frame into a matrix with n rows

[Davide Piffer]

Thanks David! It worked!

On 17 May 2017 at 23:39, David Winsemius <dwinsemius at comcast.net> wrote:
>
>> On May 17, 2017, at 1:01 PM, Davide Piffer <pifferdavide at gmail.com> wrote:
>>
>> Thanks! This gets closer to the solution but a small problem remains.
>> I get 2 rows and only one column, whereas I need a 2x2 matrix (like a
>> contingency table for Fisher's exact test).Also another issue is it
>> repeats the first number of the column, instead of using all 4.
>> For example, first vector of df is=c(564,3825,125, 377
>>
>> I get:
>>
>>         [,1]
>> [1,] 564.3112
>> [2,] 564.3112
>>
>>
>> But I should get
>>
>>       [,1]   [.2]
>> [1,]564   125
>> [2,] 3825  377
>
> ( y <- data.frame(matrix(1:40, 4, 10)) )
> ( y.mat <- lapply(y, matrix, nrow=2))
>
>> head(y.mat, 3)
> $X1
>      [,1] [,2]
> [1,]    1    3
> [2,]    2    4
>
> $X2
>      [,1] [,2]
> [1,]    5    7
> [2,]    6    8
>
> $X3
>      [,1] [,2]
> [1,]    9   11
> [2,]   10   12
>
>>
>> On 17 May 2017 at 22:35, David L Carlson <dcarlson at tamu.edu> wrote:
>>> Not really enough info here since you don't specify much about the data frame or how the results should be provided, but maybe something like this:
>>>
>>> y <- data.frame(matrix(1:100, 10, 10))
>>> y.mat <- lapply(y, matrix, nrow=2)
>>> str(y.mat)
>>> List of 10
>>> $ X1 : int [1:2, 1:5] 1 2 3 4 5 6 7 8 9 10
>>> $ X2 : int [1:2, 1:5] 11 12 13 14 15 16 17 18 19 20
>>> $ X3 : int [1:2, 1:5] 21 22 23 24 25 26 27 28 29 30
>>> $ X4 : int [1:2, 1:5] 31 32 33 34 35 36 37 38 39 40
>>> $ X5 : int [1:2, 1:5] 41 42 43 44 45 46 47 48 49 50
>>> $ X6 : int [1:2, 1:5] 51 52 53 54 55 56 57 58 59 60
>>> $ X7 : int [1:2, 1:5] 61 62 63 64 65 66 67 68 69 70
>>> $ X8 : int [1:2, 1:5] 71 72 73 74 75 76 77 78 79 80
>>> $ X9 : int [1:2, 1:5] 81 82 83 84 85 86 87 88 89 90
>>> $ X10: int [1:2, 1:5] 91 92 93 94 95 96 97 98 99 100
>>>
>>>
>>> -------------------------------------
>>> David L Carlson
>>> Department of Anthropology
>>> Texas A&M University
>>> College Station, TX 77840-4352
>>>
>>>
>>> -----Original Message-----
>>> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Davide Piffer
>>> Sent: Wednesday, May 17, 2017 2:18 PM
>>> To: r-help at r-project.org
>>> Subject: [R] converting each column of a data frame into a matrix with n rows
>>>
>>> I need to convert each vector of a dataframe into a matrix with 2 rows
>>> and 2 columns (i.e. contingency table).
>>> Note I don't want to convert the entire df into a matrix! I want to
>>> apply a function that converts each 4 elements vector of a df into a 2
>>> x 2 matrix.
>>>
>>> I wrote something like this, but it will not work:
>>>
>>> f_matrix=function(x){ matrix (x)
>>>  nrow=2}
>>> matrix_y=apply(y,2,function(x) f_matrix (x))
>>>
>>> ______________________________________________
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>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>> ______________________________________________
>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> David Winsemius
> Alameda, CA, USA
>