[R] struggling with apply

[Michael Ashton]

Always amazes me how many ways there are to do these things, none of which I was able to find myself. Thanks! I think the key here was ‘pmin,’ which I didn’t know before.

Michael Ashton, CFA
Managing Principal

Enduring Investments LLC
W: 973.457.4602
C: 551.655.8006
Schedule a Call: https://calendly.com/m-ashton

From: Bert Gunter [mailto:bgunter.4567 using gmail.com]
Sent: Wednesday, May 27, 2020 2:22 PM
To: Rui Barradas
Cc: Michael Ashton; r-help using r-project.org
Subject: Re: [R] struggling with apply

Better, I think (no indexing):

t(apply(somematrix,1,function(x)pmin(x,UB)))


Bert Gunter

"The trouble with having an open mind is that people keep coming along and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, May 27, 2020 at 10:56 AM Rui Barradas <ruipbarradas using sapo.pt<mailto:ruipbarradas using sapo.pt>> wrote:
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
> W: 973.457.4602
> C: 551.655.8006
> Schedule a Call: https://calendly.com/m-ashton
>
>
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>
> ______________________________________________
> R-help using r-project.org<mailto:R-help using r-project.org> mailing list -- To UNSUBSCRIBE and more, see
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> and provide commented, minimal, self-contained, reproducible code.
>

______________________________________________
R-help using r-project.org<mailto:R-help using r-project.org> mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

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