From: Jean Eid <jeaneid_at_chass.utoronto.ca>

Date: Wed 24 Aug 2005 - 02:01:07 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Aug 24 02:07:20 2005

Date: Wed 24 Aug 2005 - 02:01:07 EST

Although it is not as fancy as all other responses, I usually just print
the value of i first and see where it stopped. Of course this assumes you
it is stored in the main env. If it is inside a function and it is failing
I usually use the <<- operator to get it to the main env. and print it.

Here you would've seen that i stopped at 0.

Jean

On Tue, 23 Aug 2005, Gabor Grothendieck wrote:

> On 8/23/05, Ravi.Vishnu@outokumpu.com <Ravi.Vishnu@outokumpu.com> wrote:

*> > Dear All,
**> > I spent an entire evening in debugging a small, fairly simple program in R
**> > - without success. It was my Guru in Bayesian Analysis, Thomas Fridtjof,
**> > who was able to diagonose the problem. He said that it took a long time
**> > for him also to locate the problem.
**> > This program illustrates in some ways the shortcomings of the error
**> > messages that R responds with. In this case, it was quite misleading and
**> > directs attention to a location far removed the actual problem statement.
**> > Without any more introductory comments, let me directly discuss the
**> > essential problem. I am enclosing the entire program after a brief
**> > discussion.
**> >
**> > The problem arises from the following statement (nr is an integer
**> > constant) :
**> > for ( i in 1:nr-1) {.......}
**> > The unexpected problem (at least for me) is that R reads the above
**> > statement as (i in (1:nr)-1) {.....}. This makes i be initially as zero
**> > which leads to an error because the for loop in R starts from 1. The
**> > problem is easily fixed by writing the for loop as ( i in 1:(nr-1))
**> > {.......}. This would be an easy problem to fix if R directly indicates
**> > what the problem is. Instead, it gives mystifying error messages which are
**> > totally misleading. For example, to the program given below, I got the
**> > following error message (these point to commands elsewhere in the program)
**> > :
**> > Error in if ((x >= 0) & (x < s2)) return(x/2) else if ((x >= s2) & (x < :
**> >
**> > missing value where TRUE/FALSE needed
**> >
**> > I would like clarifications on the following points :
**> > 1. I am just curious to know if the priority of operators in the for
**> > statement ( the colon before the minus operator, for example) is a
**> > deliberate design decision. I have tested Matlab and found that it
**> > interprets my original statement correctly without an extra paranthesis.
**>
**> ?Syntax gives the operator precedence.
**>
**> Also, note that : is probably best not used in functions since it does
**> not handle boundary conditions properly. If n were 0 then 1:n
**> results in two iterations corresonding to 1 and 0 but what you
**> really wanted was likely no iterations at all. To do that you need
**> seq(length = n) rather than ":".
**>
**> Also I have found expressions like 0:1/10 handy to generate
**> 0, .1, .2, ..., 1 and that works with the current precedence.
**>
**> ______________________________________________
**> R-help@stat.math.ethz.ch mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
**>
*

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Aug 24 02:07:20 2005

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