# [R] creating lists of random matrices

Peter Langfelder peter.langfelder at gmail.com
Thu Nov 10 02:58:00 CET 2016

```Add a

simplify = FALSE

to the call to replicate, and you'll get a list.

replicate(5, matrix(rnorm(4), 2, 2), simplify = FALSE)

Peter

On Wed, Nov 9, 2016 at 10:45 AM, Rui Barradas <ruipbarradas at sapo.pt> wrote:
> Hello,
>
> I also thought of replicate() but it creates an 2x2x5 array, not a list.
> Maybe it's all the same for the OP.
>
> Rui Barradas
>
> Em 09-11-2016 18:41, Marc Schwartz escreveu:
>>
>>
>>> On Nov 9, 2016, at 12:32 PM, Evan Cooch <evan.cooch at gmail.com> wrote:
>>>
>>> So, its easy enough to create a random matrix, using something like (say)
>>>
>>> matrix(rnorm(4),2,2)
>>>
>>> which generates a (2x2) matrix with random N(0,1) in each cell.
>>>
>>> But, what I need to be able to do is create a 'list' of such random
>>> matrices, where the length of the list (i.e., the number of said random
>>> matrices I store in the list) is some variable I can pass to the function
>>> (or loop).
>>>
>>> I tried the obvious like
>>>
>>> hold <- list()
>>> for (i in 1:5) {
>>>     hold[[i]] <- matrix(rnorm(4),2,2)
>>>     }
>>>
>>>
>>> While this works, it seems inelegant, and I'm wondering if there is a
>>> better (more efficient) way to accomplish the same thing -- perhaps avoiding
>>> the loop.
>>>
>>> Thanks in advance...
>>
>>
>>
>> Hi,
>>
>> See ?replicate
>>
>> Example:
>>
>> ## Create a list of 5 2x2 matrices
>>
>>> replicate(5, matrix(rnorm(4), 2, 2))
>>
>> , , 1
>>
>>             [,1]      [,2]
>> [1,] -0.1695775 1.0306685
>> [2,]  0.1636667 0.1044762
>>
>> , , 2
>>
>>             [,1]      [,2]
>> [1,] -0.3098566 2.1758363
>> [2,] -0.8029768 0.9697776
>>
>> , , 3
>>
>>             [,1]      [,2]
>> [1,]  0.5702972 0.7165806
>> [2,] -0.9731331 0.8332827
>>
>> , , 4
>>
>>             [,1]       [,2]
>> [1,] -0.8089588 0.09195256
>> [2,] -0.2026994 0.67545827
>>
>> , , 5
>>
>>            [,1]       [,2]
>> [1,] 0.5093008 -0.3097362
>> [2,] 0.6467358  0.3536414
>>
>>
>> Regards,
>>
>> Marc Schwartz
>>
>>
>>         [[alternative HTML version deleted]]
>>
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>> 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.

```

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