Re: [Rd] bugfix for nls with port algorithm (PR#13540)

From: William Dunlap <wdunlap_at_tibco.com>
Date: Thu, 19 Feb 2009 12:21:53 -0800

> -----Original Message-----
> From: r-devel-bounces_at_r-project.org
> [mailto:r-devel-bounces_at_r-project.org] On Behalf Of
> Manuel.A.Morales_at_williams.edu
> Sent: Thursday, February 19, 2009 11:55 AM
> To: r-devel_at_stat.math.ethz.ch
> Cc: R-bugs_at_r-project.org
> Subject: [Rd] bugfix for nls with port algorithm (PR#13540)
>
> Full_Name: Manuel A. Morales
> Version: 2.8.1
> OS: Linux
> Submission from: (NULL) (137.165.199.246)
>
>
> When fitting a model in nls using the algorithm port with
> constraints and the
> shorthand parameter[factor] in the model, I get the following
> error message:
>
> "Error in nls_port_fit(m, start, lower, upper, control, trace) :
> (list) object cannot be coerced to type 'double'
> In addition: Warning message:
> In start < low :
> longer object length is not a multiple of shorter object length"
>
> This error can be fixed by changing line 423 in nls.R from:
>
> if(any(start < low || start > upp)) {
>
> to:
>
> if(any(unlist(start) < low || unlist(start) > upp)) {

The || should be changed to | or this should be converted to 2 calls to any() joined by a ||. (I prefer the latter.) Otherwise you get no notice that your start value is out of bounds in many cases. E.g., with your data and fix the following ought to complain:
  nls(y~b0[fac]+b1*x, start=list(b0=c(1,-1),b1=101), algorithm="port",     upper=c(100,100,100), lower=c(0,0,0)) Changing that line to
  if (any(unlist(start) < low) || any(unlist(start) > upp)) { makes it give a proper complaint:
  > nls(y~b0[fac]+b1*x, start=list(b0=c(1,-1),b1=101), algorithm="port",   + upper=c(100,100,100), lower=c(0,0,0))   Error in nls(y ~ b0[fac] + b1 * x, start = list(b0 = c(1, -1), b1 = 101), :

    Convergence failure: initial par violates constraints

Should '||' and '&&' warn if their arguments are not scalar (or perhaps 0-long also)? The related 'if' does:
  > if(c(TRUE,FALSE)) cat("yes\n") else cat("no\n")   yes
  Warning message:
  In if (c(TRUE, FALSE)) cat("yes\n") else cat("no\n") :     the condition has length > 1 and only the first element will be used

Bill Dunlap
TIBCO Software Inc - Spotfire Division
wdunlap tibco.com
>
> The following code will generate the error:
> x = runif(200)
> b0 = c(rep(0,100),runif(100))
> b1 = 1
> fac <- as.factor(rep(c(0,1), each=100))
> y = b0+b1*x+rnorm(200,sd=0.05)
> nls(y~b0[fac]+b1*x, start=list(b0=c(1,1),b1=1), algorithm="port",
> upper=c(100,100,100))
>
> Manuel
>
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>



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