[R] applying quantile to a list using values of another object as probs

[Dan Davison]

"Lorenzo Cattarino" <l.cattarino at uq.edu.au> writes:

> Hi Jim,
>
> Thanks for your reply. Your codes does work but I was hoping to find a
> way to use lapply and avoid the for loop.
>
> Lorenzo
>
>
> -----Original Message-----
> From: Jim Lemon [mailto:jim at bitwrit.com.au] 
> Sent: Monday, 17 May 2010 8:27 PM
> To: Lorenzo Cattarino
> Cc: r-help at r-project.org
> Subject: Re: [R] applying quantile to a list using values of another
> object as probs
>
> On 05/17/2010 06:01 PM, Lorenzo Cattarino wrote:
>> Hi r-users,
>>
>> I have a matrix B and a list of 3x3 matrices (mylist). I want to
>> calculate the quantiles in the list using each of the value of B as
>> probabilities.

It's a little confusing, because it isn't clear why the elements of
mylist are matrices, nor why B is a matrix. I.e. why aren't these things
just dimensionless vectors? However if you really do want to ignore the
row/column information then perhaps what you're looking for is

lapply(mylist, quantile, probs=B)

[[1]]
 26.55087%  37.21239%  57.28534%  90.82078%  20.16819%  89.83897%  94.46753%  66.07978%   62.9114% 
-0.2191315  0.3738468  0.5389231  1.2277025 -0.4274793  1.1973174  1.3405621  0.6223309  0.5811310 
 6.178627%  20.59746%  17.65568% 
-1.4270686 -0.4166326 -0.4909661 

[[2]]
   26.55087%    37.21239%    57.28534%    90.82078%    20.16819%    89.83897%    94.46753% 
-0.004930323  0.072476814  0.703609732  0.925581428 -0.027300847  0.923628895  0.932833742 
   66.07978%     62.9114%    6.178627%    20.59746%    17.65568% 
 0.793329524  0.783422677 -1.028244961 -0.026313767 -0.033078300 

[[3]]
 26.55087%  37.21239%  57.28534%  90.82078%  20.16819%  89.83897%  94.46753%  66.07978%   62.9114% 
-0.1492189 -0.1040074  0.2025300  0.8161114 -0.2803999  0.7580782  1.0316644  0.3963404  0.3886679 
 6.178627%  20.59746%  17.65568% 
-0.9801188 -0.2693299 -0.3451936 

Dan

>>
>>
>>
>> The codes I wrote are:
>>
>>
>>
>> B<- matrix (runif(12, 0, 1), 3, 4)
>>
>> mylist<- lapply(mylist, function(x) {matrix (rnorm(9), 3, 3)})
>>
>>
>>
>> for (i in 1:length(B))
>>
>> {
>>
>>    quant<- lapply (mylist, quantile, probs=B[i])
>>
>> }
>>
>>
>>
>> But quant returned the quantiles calculated using only the last value
>> ([3,3]) of the matrix B.
>>
>>
> Hi Lorenzo,
> This works for me:
>
> B<-matrix (runif(12,0,1),3,4)
> mylist<-list()
> for(i in 1:3) mylist[[i]]<-matrix(rnorm(9),3,3)
> myq<-list()
> for(i in 1:3)myq[[i]]<-quantile(mylist[[i]],probs=B[i,])
>
> Although looking at your example, I may have misunderstood what you want
>
> the result to be.
>
> Jim