Re: [R] creating lists of random matrices

[Peter Langfelder]

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  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  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.
>>
>
> __
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> and provide commented, minimal, self-contained, reproducible code.

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Re: [R] creating lists of random matrices

[Rui Barradas]

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  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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Re: [R] creating lists of random matrices

[Uwe Ligges]

Not answering the question, but if you have the same dimensions of the 
matrices everywhere, it is much more efficient to sample all numbers in 
a row and put stuff into an array:


array(rnorm(5*4), dim=c(2,2,5)))

Best,
Uwe Ligges




On 09.11.2016 19:51, Marc Schwartz wrote:



On Nov 9, 2016, at 12:41 PM, Marc Schwartz  wrote:



On Nov 9, 2016, at 12:32 PM, Evan Cooch  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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Re: [R] creating lists of random matrices

[Evan Cooch]

>>
>> 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)
>


Perfect does the trick. Thanks also for the lapply solutions from 
others. The replicate approach is more 'transparent' at least to me.

[[alternative HTML version deleted]]

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Re: [R] creating lists of random matrices

[Marc Schwartz]

> On Nov 9, 2016, at 12:41 PM, Marc Schwartz  wrote:
> 
> 
>> On Nov 9, 2016, at 12:32 PM, Evan Cooch  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


[[alternative HTML version deleted]]

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Re: [R] creating lists of random matrices

[Rui Barradas]

Hello,

Try using ?lapply, its return value is a list. Note however that the 
*apply functions are loops in disguise. There's nothing wrong with your 
solution to the problem, but it's true that most R users find lapply 
more elegant, like you say.


hold <- lapply(1:5, function(x) matrix(rnorm(4),2,2) )

Hope this helps,

Rui Barradas

Em 09-11-2016 18:32, Evan Cooch escreveu:

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...

__
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https://stat.ethz.ch/mailman/listinfo/r-help
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http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.


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Re: [R] creating lists of random matrices

[Marc Schwartz]

> On Nov 9, 2016, at 12:32 PM, Evan Cooch  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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[R] creating lists of random matrices

[Evan Cooch]

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...

__
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https://stat.ethz.ch/mailman/listinfo/r-help
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and provide commented, minimal, self-contained, reproducible code.