Aggreed. R's own way of handling logrithm of a negative number makes
scripting more automatic, which is actually desireable.
To flag any problems that might occur in calculation, do it ahead of using
logrithm or in other similar situations. Try test functions like is.nan(),
is.finite(), or relational operators like < 0, > 0.

2010/12/23 Petr PIKAL <petr.pikal@precheza.cz>

> Hi
>
> r-help-bounces@r-project.org napsal dne 23.12.2010 05:13:37:
>
> > Dear friends, hope I could be able to explain my problem through
> following
> > example. Please consider this:
> >
> >
> >
> > > set.seed(1)
> >
> > > input <- rnorm(10)
> >
> > > input
> >
> > [1] -0.6264538  0.1836433 -0.8356286  1.5952808  0.3295078 -0.8204684
> > 0.4874291  0.7383247  0.5757814 -0.3053884
> >
> > > tag <- vector(length=10)
> >
> >
> >
> > for(i in 1:10)
> >
> >     #  if there is any ****error**** in evaluating "log(input[i])" (or
> > evaluating some function) then tag[i] = 1, otherwise tag[i] = 0
> >
> >
> >
> > Therefore my "tag" vector should like: tag[1]=1, tag[2]=0, tag[3]=1,
> > tag[4]=0, tag[5]=0.......
> >
> >
> >
> > Actually R returns logarithm of a negative number as NaN, however in
> this
> > example please consider R returns error when it encounters logarithm of
> a
> > negative number.
> >
>
> I do not understand above sentence well. R returns NaN not error.
>
> For error handling in loop use try or tryCatch.
>
> For simple vectorised function evaluation as log you can use is.*
> evaluation
>
> is.nan(log(input))*1
> [1] 1 0 1 0 0 1 0 0 0 1
>
> ifelse(is.nan(log(input)), 1,0)
>  [1] 1 0 1 0 0 1 0 0 0 1
>
> Regards
> Petr
>
>
>
> >
> >
> > Is there any way to do above task?
> >
> >
> >
> > Thanks and regards,
> >
> >
> >    [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help@r-project.org mailing list
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> PLEASE do read the posting guide
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>

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