R help - Sep 2017 - building random matrices from vectors of random parameters

Thanks for both the mapply and array approaches! However, although 
intended to generate the same result, they don't:

# mapply approach

n = 3
sa <- rnorm(n,0.8,0.1)
so <- rnorm(n,0.5,0.1)
m <- rnorm(n,1.2,0.1)
mats = mapply(function(sa1, so1, m1) 
matrix(c(0,sa1*m1,so1,sa1),2,2,byrow=T), sa, so, m, SIMPLIFY = FALSE)

print(mats)

[[1]]
 ????????? [,1]????? [,2]
[1,] 0.0000000 0.8643679
[2,] 0.4731249 0.7750431

[[2]]
 ????????? [,1]????? [,2]
[1,] 0.0000000 0.8838286
[2,] 0.5895258 0.7880983

[[3]]
 ????????? [,1]????? [,2]
[1,] 0.0000000 1.1491560
[2,] 0.4947322 0.9744166


Now, the array approach:

# array approach

ms <- array(c(rep(0, 3),sa*m,so,sa), c(3, 2, 2))

for (i in 1:n) { print(ms[i,,])

 ????????? [,1]????? [,2]
[1,] 0.0000000 0.4731249
[2,] 0.8643679 0.7750431

 ????????? [,1]????? [,2]
[1,] 0.0000000 0.5895258
[2,] 0.8838286 0.7880983

 ???????? [,1]????? [,2]
[1,] 0.000000 0.4947322
[2,] 1.149156 0.9744166


These matrices are the transpose of those returned by the mapply 
approach. To see if one approach or the other is 'confused', I simply 
rerun setting sd=0 for the parameters -- thus, every matrix will be the 
same. The correct matrix would be:

 ???? [,1] [,2]
[1,]? 0.0 0.96
[2,]? 0.5 0.80


In fact, this is what is returned by the mapply approach, while the 
array approach returns the transpose. I gather the 'missing step' is to 
use aperm, but haven't figured out how to get that to work...yet.


On 9/28/2017 5:11 AM, Duncan Murdoch wrote:
> ms <- array(c(rep(0, 5),sa*m,so,sa), c(5, 2, 2)) 

	[[alternative HTML version deleted]]

>
> In fact, this is what is returned by the mapply approach, while the 
> array approach returns the transpose. I gather the 'missing step'
is
> to use aperm, but haven't figured out how to get that to work...yet.
ms <- array(c(rep(0, 3),sa*m,so,sa), c(3, 2, 2))

ms_new <- aperm(ms,c(1,3,2));

for (i in 1:n) { print(ms_new[i,,]) }

 ???? [,1] [,2]
[1,]? 0.0 0.96
[2,]? 0.5 0.80

 ???? [,1] [,2]
[1,]? 0.0 0.96
[2,]? 0.5 0.80

 ???? [,1] [,2]
[1,]? 0.0 0.96
[2,]? 0.5 0.80

>
>
> On 9/28/2017 5:11 AM, Duncan Murdoch wrote:
>> ms <- array(c(rep(0, 5),sa*m,so,sa), c(5, 2, 2)) 
>
	[[alternative HTML version deleted]]

On 28/09/2017 9:10 AM, Evan Cooch wrote:
> Thanks for both the mapply and array approaches! However, although 
> intended to generate the same result, they don't:
> 
> # mapply approach
> 
> n = 3
> sa <- rnorm(n,0.8,0.1)
> so <- rnorm(n,0.5,0.1)
> m <- rnorm(n,1.2,0.1)
> mats = mapply(function(sa1, so1, m1) 
> matrix(c(0,sa1*m1,so1,sa1),2,2,byrow=T), sa, so, m, SIMPLIFY = FALSE)
> 
> print(mats)
> 
> [[1]]
>  ????????? [,1]????? [,2]
> [1,] 0.0000000 0.8643679
> [2,] 0.4731249 0.7750431
> 
> [[2]]
>  ????????? [,1]????? [,2]
> [1,] 0.0000000 0.8838286
> [2,] 0.5895258 0.7880983
> 
> [[3]]
>  ????????? [,1]????? [,2]
> [1,] 0.0000000 1.1491560
> [2,] 0.4947322 0.9744166
> 
> 
> Now, the array approach:
> 
> # array approach
> 
> ms <- array(c(rep(0, 3),sa*m,so,sa), c(3, 2, 2))
> 
> for (i in 1:n) { print(ms[i,,])
> 
>  ????????? [,1]????? [,2]
> [1,] 0.0000000 0.4731249
> [2,] 0.8643679 0.7750431
> 
>  ????????? [,1]????? [,2]
> [1,] 0.0000000 0.5895258
> [2,] 0.8838286 0.7880983
> 
>  ???????? [,1]????? [,2]
> [1,] 0.000000 0.4947322
> [2,] 1.149156 0.9744166
> 
> 
> These matrices are the transpose of those returned by the mapply 
> approach. To see if one approach or the other is 'confused', I
simply
> rerun setting sd=0 for the parameters -- thus, every matrix will be the 
> same. The correct matrix would be:
> 
>  ???? [,1] [,2]
> [1,]? 0.0 0.96
> [2,]? 0.5 0.80
> 
> 
> In fact, this is what is returned by the mapply approach, while the 
> array approach returns the transpose. I gather the 'missing step'
is to
> use aperm, but haven't figured out how to get that to work...yet.
> 
> 
> On 9/28/2017 5:11 AM, Duncan Murdoch wrote:
>> ms <- array(c(rep(0, 5),sa*m,so,sa), c(5, 2, 2)) 
> 

Sorry about that -- I didn't notice the "byrow = T" in your
original.

Duncan Murdoch

Sure -- thanks -- only took me 3-4 attempts to get aperm to work (as 
opposed to really thinking hard about how it works ;-)

On 9/28/2017 11:55 AM, Duncan Murdoch wrote:
> On 28/09/2017 9:10 AM, Evan Cooch wrote:
>> Thanks for both the mapply and array approaches! However, although 
>> intended to generate the same result, they don't:
>>
>> # mapply approach
>>
>> n = 3
>> sa <- rnorm(n,0.8,0.1)
>> so <- rnorm(n,0.5,0.1)
>> m <- rnorm(n,1.2,0.1)
>> mats = mapply(function(sa1, so1, m1) 
>> matrix(c(0,sa1*m1,so1,sa1),2,2,byrow=T), sa, so, m, SIMPLIFY = FALSE)
>>
>> print(mats)
>>
>> [[1]]
>> ?????????? [,1]????? [,2]
>> [1,] 0.0000000 0.8643679
>> [2,] 0.4731249 0.7750431
>>
>> [[2]]
>> ?????????? [,1]????? [,2]
>> [1,] 0.0000000 0.8838286
>> [2,] 0.5895258 0.7880983
>>
>> [[3]]
>> ?????????? [,1]????? [,2]
>> [1,] 0.0000000 1.1491560
>> [2,] 0.4947322 0.9744166
>>
>>
>> Now, the array approach:
>>
>> # array approach
>>
>> ms <- array(c(rep(0, 3),sa*m,so,sa), c(3, 2, 2))
>>
>> for (i in 1:n) { print(ms[i,,])
>>
>> ?????????? [,1]????? [,2]
>> [1,] 0.0000000 0.4731249
>> [2,] 0.8643679 0.7750431
>>
>> ?????????? [,1]????? [,2]
>> [1,] 0.0000000 0.5895258
>> [2,] 0.8838286 0.7880983
>>
>> ????????? [,1]????? [,2]
>> [1,] 0.000000 0.4947322
>> [2,] 1.149156 0.9744166
>>
>>
>> These matrices are the transpose of those returned by the mapply 
>> approach. To see if one approach or the other is 'confused', I
simply
>> rerun setting sd=0 for the parameters -- thus, every matrix will be 
>> the same. The correct matrix would be:
>>
>> ????? [,1] [,2]
>> [1,]? 0.0 0.96
>> [2,]? 0.5 0.80
>>
>>
>> In fact, this is what is returned by the mapply approach, while the 
>> array approach returns the transpose. I gather the 'missing
step' is
>> to use aperm, but haven't figured out how to get that to
work...yet.
>>
>>
>> On 9/28/2017 5:11 AM, Duncan Murdoch wrote:
>>> ms <- array(c(rep(0, 5),sa*m,so,sa), c(5, 2, 2)) 
>>
>
>
> Sorry about that -- I didn't notice the "byrow = T" in your
original.
>
> Duncan Murdoch
>

	[[alternative HTML version deleted]]