Dear list A strange bug in the psych package is due to the behavior of the diag function: It gives the expected values for 1, a vector (-1,1), but not for -1 Is this a known feature?> diag(1)[,1] [1,] 1> diag(c(-1,1))[,1] [,2] [1,] -1 0 [2,] 0 1> diag(-1)Error in diag(-1) : invalid 'nrow' value (< 0) Bill William Revelle personality-project.org/revelle.html Professor personality-project.org Department of Psychology www.wcas.northwestern.edu/psych/ Northwestern University www.northwestern.edu/ Use R for psychology personality-project.org/r It is 2 minutes to midnight www.thebulletin.org
On 17/09/2018 12:14 PM, William Revelle wrote:> Dear list > > A strange bug in the psych package is due to the behavior of the diag function: > > It gives the expected values for 1, a vector (-1,1), but not for -1 > > Is this a known feature?It is pretty clearly documented: "diag has four distinct usages: ... 3. x is a scalar (length-one vector) and the only argument, it returns a square identity matrix of size given by the scalar." Duncan Murdoch> > >> diag(1) > [,1] > [1,] 1 >> diag(c(-1,1)) > [,1] [,2] > [1,] -1 0 > [2,] 0 1 >> diag(-1) > Error in diag(-1) : invalid 'nrow' value (< 0) > > > Bill > > > William Revelle personality-project.org/revelle.html > Professor personality-project.org > Department of Psychology www.wcas.northwestern.edu/psych/ > Northwestern University www.northwestern.edu/ > Use R for psychology personality-project.org/r > It is 2 minutes to midnight www.thebulletin.org > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >
I would say it is a mis-feature. If the 'x' argument of diag() is a
vector of length 1, then it creates an identity matrix of that size,
instead of creating a 1x1 matrix with the given value:
? diag(3)
[,1] [,2] [,3]
[1,] 1 0 0
[2,] 0 1 0
[3,] 0 0 1
Of course this makes it cumbersome to use diag() in a package, when
you are not sure if the input vector is longer than 1. This seems to
be a good workaround:
? diag(-1, nrow = 1)
[,1]
[1,] -1
Or, in general if you have vector v:
? v <- -1
? diag(v, nrow = length(v))
[,1]
[1,] -1
Gabor
On Mon, Sep 17, 2018 at 5:14 PM William Revelle <lists at revelle.net>
wrote:>
> Dear list
>
> A strange bug in the psych package is due to the behavior of the diag
function:
>
> It gives the expected values for 1, a vector (-1,1), but not for -1
>
> Is this a known feature?
>
>
> > diag(1)
> [,1]
> [1,] 1
> > diag(c(-1,1))
> [,1] [,2]
> [1,] -1 0
> [2,] 0 1
> > diag(-1)
> Error in diag(-1) : invalid 'nrow' value (< 0)
>
>
> Bill
>
>
> William Revelle personality-project.org/revelle.html
> Professor personality-project.org
> Department of Psychology www.wcas.northwestern.edu/psych/
> Northwestern University www.northwestern.edu/
> Use R for psychology personality-project.org/r
> It is 2 minutes to midnight www.thebulletin.org
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
It behaves as per documentation.
" Using diag(x) can have unexpected effects if x is a vector that could be
of length one. Use diag(x, nrow = length(x)) for consistent behavior."
Ravi
________________________________
From: R-devel <r-devel-bounces at r-project.org> on behalf of G?bor Cs?rdi
<csardi.gabor at gmail.com>
Sent: Monday, September 17, 2018 12:22:31 PM
To: lists at revelle.net
Cc: r-devel
Subject: Re: [Rd] diag(-1) produces weird result
I would say it is a mis-feature. If the 'x' argument of diag() is a
vector of length 1, then it creates an identity matrix of that size,
instead of creating a 1x1 matrix with the given value:
? diag(3)
[,1] [,2] [,3]
[1,] 1 0 0
[2,] 0 1 0
[3,] 0 0 1
Of course this makes it cumbersome to use diag() in a package, when
you are not sure if the input vector is longer than 1. This seems to
be a good workaround:
? diag(-1, nrow = 1)
[,1]
[1,] -1
Or, in general if you have vector v:
? v <- -1
? diag(v, nrow = length(v))
[,1]
[1,] -1
Gabor
On Mon, Sep 17, 2018 at 5:14 PM William Revelle <lists at revelle.net>
wrote:>
> Dear list
>
> A strange bug in the psych package is due to the behavior of the diag
function:
>
> It gives the expected values for 1, a vector (-1,1), but not for -1
>
> Is this a known feature?
>
>
> > diag(1)
> [,1]
> [1,] 1
> > diag(c(-1,1))
> [,1] [,2]
> [1,] -1 0
> [2,] 0 1
> > diag(-1)
> Error in diag(-1) : invalid 'nrow' value (< 0)
>
>
> Bill
>
>
> William Revelle personality-project.org/revelle.html
> Professor personality-project.org
> Department of Psychology
www.wcas.northwestern.edu/psych/<http://www.wcas.northwestern.edu/psych/>
> Northwestern University
www.northwestern.edu/<http://www.northwestern.edu/>
> Use R for psychology personality-project.org/r
> It is 2 minutes to midnight
www.thebulletin.org<http://www.thebulletin.org>
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
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