[R] creating lists of random matrices

[Marc Schwartz]

> On Nov 9, 2016, at 12:41 PM, Marc Schwartz <marc_schwartz at me.com> wrote:
> 
> 
>> 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



Sorry, correction on my reply.

I copied the wrong output, It should be:

> replicate(5, matrix(rnorm(4), 2, 2), simplify = FALSE)
[[1]]
          [,1]      [,2]
[1,] 0.9700486 1.4249251
[2,] 0.7621312 0.8267747

[[2]]
          [,1]       [,2]
[1,] 0.4517927  0.2047509
[2,] 0.6336959 -0.6028124

[[3]]
          [,1]      [,2]
[1,] 0.6468823 0.4268734
[2,] 0.1664907 0.3905180

[[4]]
           [,1]       [,2]
[1,] -0.3170839 -1.0113201
[2,] -1.5356600  0.9658132

[[5]]
           [,1]       [,2]
[1,] -1.1937503 -0.2653502
[2,]  0.9319919  0.1780254


The 'simplify' argument should be FALSE, so that an array is not created.

Regards,

Marc Schwartz


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