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casperyc

2012-May-16 21:09 UTC

[R] triangular matrices input/output

Hi,

Is there any package that deals with triangular matrices?

Say ways of inputting an upper (lower) triangular matrix?

Or convert a vector of length 6 to an upper (lower) triangular matrix (by
row/column)?

Thanks!

-----
######################
PhD candidate in Statistics
Big R Fan
Big LEGO Fan
Big sTaTs Fan
######################

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R. Michael Weylandt

2012-May-16 23:41 UTC

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[R] triangular matrices input/output

The Matrix package provides good support for many special sorts of
matrices, but here it looks like you probably don't need that
additional machinery for such small case:

makeUpper <- function(vec, diag = FALSE){
    n <- (-1 + sqrt(1 + 8*length(vec)))/2
    stopifnot(isTRUE(all.equal(n, as.integer(n))))

    if(!diag) n <- n + 1

    mat <- matrix(0, ncol = n, nrow = n)
    mat[upper.tri(mat, diag)] <- vec
    mat
}

I think does what you want and it's not too hard to generalize to
lower triangular.

E.g.,

v <- 1:6
makeUpper(v)
makeUpper(v, diag = TRUE)

It's not super well tested though so caveat lector.

Michael

On Wed, May 16, 2012 at 5:09 PM, casperyc <casperyc at hotmail.co.uk>
wrote:> Hi,
>
> Is there any package that deals with triangular matrices?
>
> Say ways of inputting an upper (lower) triangular matrix?
>
> Or convert a vector of length 6 to an upper (lower) triangular matrix (by
> row/column)?
>
> Thanks!
>
> -----
> ######################
> PhD candidate in Statistics
> Big R Fan
> Big LEGO Fan
> Big sTaTs Fan
> ######################
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/triangular-matrices-input-output-tp4630310.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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.

R. Michael Weylandt <michael.weylandt@gmail.com>

2012-May-17 00:26 UTC

head link

[R] triangular matrices input/output

Do leave the posts for anyone else who might google the same question. (I
don't think you really could delete the post anyways, perhaps only on one
mirror)

You could probably use some combination or rev() and t() to fill by row, but I
haven't thought through the geometry all the way yet.

Michael 

On May 16, 2012, at 8:13 PM, YUProf <casperyc@hotmail.co.uk> wrote:
> Hi Michael,
> 
> I have figured out a 'super' easy way myself and already deleted
the post.
> 
> It can be done using: (no package necssary)
> 
> d=c(3,6,2,1,4,5)
> x=matrix(,3,3)
> 
> # by column, 
> x[!lower.tri(x)]=d
> 
> I am still trying very hard to think of a way to fit it by row as I
sometimes have to!
> 
> THANKS!
> 
> Chen
> 
>
=============================================================================>
Mr Chen YU
> PhD candidate in Statistics
> School of Mathematics, Statistics and Actuarial Science, University of Kent
> 
> D7/D Woolf College, The Pavilion, Giles Lane, Canterbury, Kent CT2 7BQ
> Mobile: +44(0)7725003559
>
=============================================================================>
> > From: michael.weylandt@gmail.com
> > Date: Wed, 16 May 2012 19:41:36 -0400
> > Subject: Re: [R] triangular matrices input/output
> > To: casperyc@hotmail.co.uk
> > CC: r-help@r-project.org
> > 
> > The Matrix package provides good support for many special sorts of
> > matrices, but here it looks like you probably don't need that
> > additional machinery for such small case:
> > 
> > makeUpper <- function(vec, diag = FALSE){
> > n <- (-1 + sqrt(1 + 8*length(vec)))/2
> > stopifnot(isTRUE(all.equal(n, as.integer(n))))
> > 
> > if(!diag) n <- n + 1
> > 
> > mat <- matrix(0, ncol = n, nrow = n)
> > mat[upper.tri(mat, diag)] <- vec
> > mat
> > }
> > 
> > I think does what you want and it's not too hard to generalize to
> > lower triangular.
> > 
> > E.g.,
> > 
> > v <- 1:6
> > makeUpper(v)
> > makeUpper(v, diag = TRUE)
> > 
> > It's not super well tested though so caveat lector.
> > 
> > Michael
> > 
> > On Wed, May 16, 2012 at 5:09 PM, casperyc
<casperyc@hotmail.co.uk> wrote:
> > > Hi,
> > >
> > > Is there any package that deals with triangular matrices?
> > >
> > > Say ways of inputting an upper (lower) triangular matrix?
> > >
> > > Or convert a vector of length 6 to an upper (lower) triangular
matrix (by
> > > row/column)?
> > >
> > > Thanks!
> > >
> > > -----
> > > ######################
> > > PhD candidate in Statistics
> > > Big R Fan
> > > Big LEGO Fan
> > > Big sTaTs Fan
> > > ######################
> > >
> > > --
> > > View this message in context:
http://r.789695.n4.nabble.com/triangular-matrices-input-output-tp4630310.html
> > > Sent from the R help mailing list archive at Nabble.com.
> > >
> > > ______________________________________________
> > > R-help@r-project.org mailing list
> > > 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.
	[[alternative HTML version deleted]]

Rui Barradas

2012-May-17 00:33 UTC

head link

[R] triangular matrices input/output

Hello,

I needed this once.

upper.diag <- function(x, byrow=FALSE){
	m <- sqrt(1 + 8*length(x))
	if(abs(m - floor(m)) <  .Machine$double.eps^0.5)
		m <- (m - 1)/2
	else{
		warning("length of 'x' is not a triangular number.")
		m <- floor((m - 1)/2)
	}
	y <- matrix(0, nrow=m, ncol=m)
	if(byrow){
		y[lower.tri(y, TRUE)] <- x
		y <- t(y)
	}else
		y[upper.tri(y, TRUE)] <- x
	y
}

lower.diag <- function(x, byrow=FALSE){
	m <- sqrt(1 + 8*length(x))
	if(abs(m - floor(m)) <  .Machine$double.eps^0.5)
		m <- (m - 1)/2
	else{
		warning("length of 'x' is not a triangular number.")
		m <- floor((m - 1)/2)
	}
	y <- matrix(0, nrow=m, ncol=m)
	if(byrow){
		y[upper.tri(y, TRUE)] <- x
		y <- t(y)
	}else
		y[lower.tri(y, TRUE)] <- x
	y
}

lower.diag(1:6)
lower.diag(1:10, TRUE)
lower.diag(1:8)

upper.diag(1:6)
upper.diag(1:10, TRUE)
upper.diag(1:12)

Hope this helps,

Rui Barradas

casperyc wrote> 
> Hi,
> 
> Is there any package that deals with triangular matrices?
> 
> Say ways of inputting an upper (lower) triangular matrix?
> 
> Or convert a vector of length 6 to an upper (lower) triangular matrix (by
> row/column)?
> 
> Thanks!
> 
> -----
> ######################
> PhD candidate in Statistics
> Big R Fan
> Big LEGO Fan
> Big sTaTs Fan
> ######################
> 
> --
> View this message in context:
>
http://r.789695.n4.nabble.com/triangular-matrices-input-output-tp4630310.html
> Sent from the R help mailing list archive at Nabble.com.
> 
> ______________________________________________
> R-help@ mailing list
> 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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View this message in context:
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