[R] Logical inconsistency

Berwin A Turlach berwin at maths.uwa.edu.au
Mon Dec 8 11:12:54 CET 2008

G'day Wacek,

On Sun, 07 Dec 2008 21:09:36 +0100
Wacek Kusnierczyk <Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:

> g'evening.

Not the done thing.
> c'mon, a person from central europe can't possibly be unaware of this
> joke.  

I wouldn't call Norway central Europe, but then I also guess that you
are not really Norwegian.

> i know of a 60-page book collecting radio erewan jokes.  deadly
> serious.

That would make you more of an expert in these kind of jokes than me.

> > Classical Radio Eriwan stuff, and I thought this class of jokes have
> > died out.....
> apparently not, as long as there are people able to find them in
> whatever they read.

Not in whatever they read.  There are necessary ingredients as you, as
an expert on Radio Eriwan, should now.  There has to be the phrase "in
principle" and something self-contradictory.  Plenty of things are
written that could not possibly be interpreted as Radio Eriwan jokes.
> > First, I think it is a rather ambitious jump in logic that a user is
> > interested in stats because the user wants to see whether "8.3 -
> > 7.3 > 1" is true.  The only indication of the user being interested
> > in stats would be that the user used R, which is used primarily for
> > statistical analysis; 
> that was my reasoning, good god!

And as I said, probably a huge jump in logic and faith.
> i'd agree that it's not a drawback to know how arithmetic is actually
> done on computers (but hey, there is no unique standard here).  but
> many people i know (which certainly makes a poor statistic) would
> prefer to be abstracted away from having to know that 8.8-7.8 > 1 is
> true, less so why it is true.

Well, these people should probably stick to pencil and paper.  Or use
an appropriate tool.  As I mentioned to you in another thread, a good
handyman does not blame his/her tools but selects the correct tool for
the job.

If I need dynamic memory allocation, I do not choose to use FORTRAN77
but some other language.  If I need infinite precision arithmetic, then
I do not choose R/Matlab/Scilab/Octave but some other tool. 

> not difficult at all to define an arithmetic where 1==0 is true,
> document it in a man page, and refer to it when complaints come. 
> surely, an exotic example.

You forget the bit that you first would have to convince some people
that this is a useful arithmetic and have them start using it.  And I
am not convinced about the "not difficult" part anyway.....
> i know of cs guys who either have forgotten, or have never learned
> (!). 

I am not surprised about CS guys never learning about these issues.  As
long as you play around with data bases (their organisation &c),
sorting algorithms, artificial intelligence (at least when I attended a
lecture on this) you do not need to know about these issues.  And,
unfortunately, it seems nowadays a lot of teaching is on a
"need-to-know" and "just-in-time" basis.  

It just became criminal when CS guys who were into compiler design
started to construct compilers that analysed the code and rearranged
the calculations based on an analysis that assumed infinite precision
arithmetic.  Such compilers optimised away code that was designed to
deal with finite precision arithmetic.  I believe this was one of the
motivations of Goldberg's article.



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