[R] struggling with apply

[Rui Barradas]

Hello,

Try pmin. And loop by column/UB index with sapply/seq_along.


sapply(seq_along(UB), function(i) pmin(UB[i], somematrix[,i]))
#     [,1] [,2] [,3] [,4]
#[1,]  1.0  5.5  8.5  7.0
#[2,]  2.5  3.0  8.0 10.5
#[3,]  2.5  5.5  5.0 10.5


Hope this helps,

Rui Barradas


Às 18:46 de 27/05/20, Michael Ashton escreveu:
> Hi -
> 
> I have a matrix of n rows and 4 columns.
> 
> I want to cap the value in each column by a different upper bound. So, suppose my matrix is
> 
> somematrix <- matrix(c(1,4,3,6,3,9,12,8,5,7,11,11),nrow=3,ncol=4)
>> somematrix
>       [,1] [,2] [,3] [,4]
> [1,]    1    6   12    7
> [2,]    4    3    8   11
> [3,]    3    9    5   11
> 
> Now I want to have the maximum value in each column described by
> UB=c(2.5, 5.5, 8.5, 10.5)
> 
> So that the right answer will look like:
>       [,1]      [,2]    [,3]   [,4]
> [1,]    1      5.5     8.5    7
> [2,]    2.5    3        8     10.5
> [3,]    2.5   5.5      5    10.5
> 
> I've tried a few things, like:
> newmatrix <- apply(somematrix,c(1,2),function(x) min(UB,x))
> 
> but I can't figure out to apply the relevant element of the UB list to the right element of the matrix. When I run the above, for example, it takes min(UB,x) over all UB, so I get:
> 
> newmatrix
>       [,1] [,2] [,3] [,4]
> [1,]  1.0  2.5  2.5  2.5
> [2,]  2.5  2.5  2.5  2.5
> [3,]  2.5  2.5  2.5  2.5
> 
> I'm sure there's a simple and elegant solution but I don't know what it is!
> 
> Thanks in advance,
> 
> Mike
> 
> Michael Ashton, CFA
> Managing Principal
> 
> Enduring Investments LLC
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