Hi Alasdair,
You'll have to summarise ;)
Rui
> -----Original Message-----
> From: [log in to unmask] [mailto:[log in to unmask]] On
> Behalf Of Alasdair Turner
> Sent: 20 December 2005 10:54
> To: [log in to unmask]
> Subject: Re: [SPACESYNTAX] RA or RRA
>
> Indeed, Mike, and Lucas, and Sheep, and Bin (and everyone else
> developing software) -- each of us has a responsibility to communicate
> what are our software does. That's probably an academic duty, but I
> think for most of us it is natural to try to do.
>
> However, I believe we need more than graph theoretic formulae to
> communicate precisely what we mean: natual language, mathematical
> formulae, and pseudo-code all have their place. One thing that
> frustrates me is the limitation of mathematical formulae when it comes
> to describe, for example, a procedural optimisation in the code. I also
> feel that formulae often obfuscate simple procedures, and so I
> personally often prefer pseudo-code. Of course, the only way someone
> can really verify what the program actually does is to read the source
> code, which returns to an argument about open source, but also raises
> the problem of when we say the code does one thing, and in fact it does
> not (e.g., a bug in Depthmap recently confused log base 10 and log base
> e -- natural to do as in C++ 'log' means log base e, wheras
> conventionally in mathematics, it means log base 10, and ln means log
> base e -- had the code been open source, any one could have spotted
> this, but the formula alone would not have sufficed, dutifully
> transcribing the 'log').
>
> As for 'the counting from 0', I started out programming in Fortran, and
> although I prefer C++, I have nothing in particular for or against
> 0-based indexing. However, the reasons for the radius difference do not
> concern zero indexing, but whether you say a radius is measured in nodes
> or steps.
>
> Alan shows the justification well with VGA, which is indeed how it
> happened, but I happen to think this definition also fits logically into
> axial analysis: I view radius as a 'distance' (albeit a step distance)
> and therefore it's units to my mind should be steps. The same applies
> in angular analysis, where I see radius as a sum of angles rather than a
> number of nodes.
>
> Finally, in case anyone is concerned that this information is only
> contained in a web discussion: the radius used in Depthmap is (I hope
> clearly) explained in the Depthmap manual.
>
> Alasdair
>
> Michael Batty wrote:
> > this conversation is almost making me look at my own software - I have
> > always assumed that there are many formulas in space syntax that were
> > not well formulated originally, and that these issues are resolved when
> > programmed. For example the definition of integration in the Social
> > Logic of Space is not in the reciprocal form that is needed when one
> > speaks of high or low integration but this gets corrected in the
> > software. Time for some standard graph theoretic statements I think of
> > all the formulas used
> >
> > Mike
> >
> > At 13:37 19/12/2005, Lucas Figueiredo wrote:
> >
> >> Hello Sheep.
> >>
> >> No one is counting from 0. A single topological step means depth 1.
> >> There is no topological step from a given line to itself.
> >>
> >> I know that arrays are confusing in some old programming languages (I
> >> also programmed in ANSI C and Pascal) and sometimes we are obliged to
> >> change outputs because such limitations of data structure.
> >>
> >> However, I read lots of papers using R3 and I always understood this
> >> radius as 3 steps away, not 2. I also think that in my MSc
> >> dissertation wrote that R3 (3 steps) is the local standard radius
> >> (which is wrong).
> >>
> >> These things (interpretations, implementations) must be clear.
> >>
> >> That is why I reinforce that academic software must be properly
> >> published AND cited - because it is part of the methodology you use in
> >> experiments. I think we must put it in our software licence "cite it,
> >> otherwise do not use it".
> >>
> >> Regards!
> >> Lucas
> >>
> >>
> >>
> >> On 19/12/05, Nick Dalton <[log in to unmask]> wrote:
> >> > Hi the code in axman was designed to be output compatible with the
> >> > fortran code. as a 'C' programmer I found it an odd switch ( and
> >> > still do).
> >> >
> >> > People typically count from one (1,2,3,4) it's only C programmers (
> >> > and their children) that count from 0. Fortran and Pascal (object
> >> > pascal being the language of Axman) use 1 based indexs for arrays and
> >> > so number systems. Everything also had to be compatible with the
> >> > output of the social logic of space ( with the D value).
> >> >
> >> > Zero depth makes sense to me but non programmers got there first.
> >> >
> >> > so R2 = r3, r3=r4 and r2=r1, which can be said to eliminate a
> >> problem ( no r1).
> >> >
> >> > Using R2 (ie old R3 )You may noticed more glitches in radius 2 due to
> >> > poor micro-structure.
> >> >
> >> > sheep
> >> >
> >> > >Dear Lucas,
> >> > >
> >> > >Yes, this is the same in Depthmap: R2 is the equivalent of R3 in
axman.
> >> > >
> >> > >I have always said that this makes sense: two steps away is to my
> >> > >mind R2, not R3.
> >> > >
> >> > >As for handling low numbers of lines within (Depthmap's) radius two,
> >> > >undefined values (nulls) are given in the (small number of) cases
> >> > >where there are too few lines to calculate RRA.
> >> > >
> >> > >Alasdair
> >> > >
> >> >
> >
> >
> > Michael Batty Director Centre for Advanced Spatial Analysis (CASA)
> > University College London - 1-19 Torrington Place - London - WC1E 6BT UK
> > _______________________________________________________________
> >
> > tel 44 (0) 207 679 1781 fax 44 (0) 207 813 2843 mobile 44 (0) 7768 423
656
> >
> > */_Personal Web Page_/* *.*
http://www.casa.ucl.ac.uk/people/MikesPage.htm
> > */_Recent Books_/* *.** /Cities and Complexity/ . *
> > http://www.complexcity.info/
> > */GIS, Spatial Analysis and Modeling/* *.*
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> >
> >
> >
> >
>
> --
> Alasdair Turner
> Course Director
> MSc Adaptive Architecture and Computation
> Bartlett School of Graduate Studies
> UCL Gower Street LONDON WC1E 6BT
>
> http://www.aac.bartlett.ucl.ac.uk/
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