Re: [R] ipop (kernlab) gives pars < lower bound ?

From: Alexis Diamond <alexisjdiamond_at_gmail.com>
Date: Wed 19 Oct 2005 - 14:11:30 EST

hi again,

i have fixed some of the problems i emailed about previously-- the answer is to fiddle with the "margin" variable. but new problems have arisen: when i set the "margin" variable appropriately to preclude negative values, i get the following error message:

Error in drop(.Call("La_dgesv", a, as matrix(b), tol, PACKAGE = "base")) : system is comptuationally singular: reciprocal condition number = 1.57163 e-16

and i was wondering if there's anything i can do about it, or if my data is just not good for this problem.

also, i am still curious about
(1) how to use ipop's "bound" argument

(2) what should i make of the warning message discussed below?

thanks again,

alexis

On 10/18/05, Alexis Diamond <alexisjdiamond@gmail.com> wrote:
> hi everyone,
>
> ipop very quickly and accurately identifies the correct parameters in
> a toy dataset i built, but when i use ipop on the real dataset i get
> values for the parameters " primal(res) " that are less than zero,
> even though i specify zero for the lower bound : l = rep(0,
> length(c)) , where length(c) is the number of parameters i'm trying to
> identify.
>
> the parameters are not A LOT less than zero-- they're close to zero,
> but still too large a problem to ignore. (eg., i get a value X1 =
> -0.006 -- it wouldn't be a problem if X1 was btw -1 e-5 and zero, but
> it's not.)
> can anyone suggest a remedy?
>
> i'm wondering if this could be caused by where i've set my "range" and
> my "bound". i've played a little with range, but it hasn't helped. i
> don't know how to use "bound"-- i don't understand the info on "bound"
> on the ipop Rhelp page.
> "sigf" is at default 7 sig figs, and the negative numbers are not
> within that threshold of zero.
>
> i'm also wondering if this problem could be related to the warning
> messages i receive when i run ipop :
>
> Warning:
> number of columns of result
> not a multiple of vector length (arg 2) in: rbind(rho, tau, alpha, nu)
>
> i get this warning message in both the toy dataset and the real
> dataset, though as i mentioned i only get negative (illegal) parameter
> values with the real dataset.
> i don't know why i get this message, or what to do about it.
>
> any advice is very much appreciated!
>
> alexis
>



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