[visit-developers] expressions question

Eric Brugger brugger1 at llnl.gov
Fri May 8 11:19:32 EDT 2009


Have you tried changing "gt" to "ge". I assume that with the expression that
you are showing, if u is equal to zero it will still try to take the 
log, which is bad.


At 07:55 AM 5/8/2009, Kathleen S. Bonnell wrote:
>Hi All,
>I'm attempting this:
>newvar = if(gt(u, 0), ln(u), -1e100)
>so that I can take the ln even though there are non-positive
>values in u.
>I guess my thinking is wrong here because the NaturalLogExpression
>gives me an error on the values <= 0
>Is there another way to get what I want?  (besides scaling the
>values beforehand?)
>If not, perhaps we could add an optional argument for ln  that
>specifies a default value to be used in place of log of values <= 0???
>Thanks for the input,

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