Re: handling NaN

[Paul Kienzle]

Or you can use nanmax as defined in octave-forge (http://octave.sf.net),
which does the same thing:

## [v, idx] = nanmax(X [, dim]);
## nanmax is identical to the max function except that NaN values are
## treated as -Inf, and so are ignored.  If all values in a column are 
## NaN, the maximum is returned as NaN.
##
## See also: nansum, nanmin, nanmean, nanmedian
function [v, idx] = nanmax (X, ...)
  if nargin < 1
    usage ("[v, idx] = nanmax(X [, dim])");
  else
    nanvals = isnan(X);
    X(nanvals) = -Inf;
    [v,idx] = max (X, all_va_args);
    v(all(nanvals, all_va_args)) = NaN;
  endif
endfunction

Paul Kienzle
address@hidden

On Tue, Jul 30, 2002 at 06:16:51PM -0500, Thomas S. Shores wrote:
> Heber Farnsworth wrote:
> 
> > I'm have trouble with NaN values.  I don't mind that they come up
> > occasionally but I need to know how to get rid of them.  I'm evaluating
> > a function at various points and I need to pick the maximum point.
> > Occasionally the point will be an illegal one and it's difficult to
> > predict when that will happen.  Obviously I don't want that point.
> > However the following behavior of octave makes it difficult to get the
> > point I do want.
> >
> > $ octave -q
> > octave:1> f = [1 2 3 NaN]
> > f =
> >
> >     1    2    3  NaN
> >
> > octave:2> max(f)
> > ans = NaN
> > octave:3> min(f)
> > ans = NaN
> > octave:4>
> >
> > If NaN is both the min and max of any vector it is contained in then how
> > do I get octave to return the value I want (3 in this case)?
> >
> > Heber
> >
> > -------------------------------------------------------------
> > Octave is freely available under the terms of the GNU GPL.
> >
> > Octave's home on the web:  http://www.octave.org
> > How to fund new projects:  http://www.octave.org/funding.html
> > Subscription information:  http://www.octave.org/archive.html
> > -------------------------------------------------------------
> 
> Try removing the NaNs first, e.g.,
> 
> f = [1 2 3 NaN]
> max(f(!isnan(f)))
> min(f(!isnan(f)))
> 
> Hope this helps
> 
> Tom Shores
> 
> 
> 
> 
> 
> -------------------------------------------------------------
> Octave is freely available under the terms of the GNU GPL.
> 
> Octave's home on the web:  http://www.octave.org
> How to fund new projects:  http://www.octave.org/funding.html
> Subscription information:  http://www.octave.org/archive.html
> -------------------------------------------------------------
> 



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------