[R-sig-Geo] problems with dnearneigh of spdep

[Stephane DRAY]

My version :

 > version
          _
platform i386-pc-mingw32
arch     i386
os       mingw32
system   i386, mingw32
status
major    1
minor    9.1
year     2004
month    06
day      21
language R
 > spdep()
[1] "spdep, version 0.2-18, 2004-05-25"
 > sum(card(mydnn))
[1] 9896
 > all(sapply(mydnn, length) == 99)
[1] FALSE

It is not the last one, I will try to update later. I think that the 
problem is in the calculation of neighbors. Perhaps, the fortran code has 
changed. I do not have the sources, so  I could not verify.

Thanks !



At 13:01 29/10/2004, Roger Bivand wrote:
>On Fri, 29 Oct 2004, Stephane DRAY wrote:
>
> > Hello,
> > I have some strange results with the dnearneigh function.
> > I would like to have all points of grid linked. I do something like that:
> >
> >  > xy=expand.grid(1:10,1:10)
> >  > mydnn=dnearneigh(as.matrix(xy),d1=0,d2=50)
> >  > mydnn
> > Neighbour list object:
> > Number of regions: 100
> > Number of nonzero links: 9896
> > Percentage nonzero weights: 98.96
> > Average number of links: 98.96
> > I assume to have 100*100-100=9900 links.
> >
> >  > m01=nb2mat(mydnn,style="B")
> >  > apply(m01,1,sum)
> >    1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18
> > 19  20  21  22  23  24  25  26  27
> >   98  99  99  99  99  99  99  99  99  98  99  99  99  99  99  99  99  99
> > 99  99  99  99  99  99  99  99  99
> >   28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45
> > 46  47  48  49  50  51  52  53  54
> >   99  99  99  99  99  99  99  99  99  99  99  99  99  99  99  99  99  99
> > 99  99  99  99  99  99  99  99  99
> >   55  56  57  58  59  60  61  62  63  64  65  66  67  68  69  70  71  72
> > 73  74  75  76  77  78  79  80  81
> >   99  99  99  99  99  99  99  99  99  99  99  99  99  99  99  99  99  99
> > 99  99  99  99  99  99  99  99  99
> >   82  83  84  85  86  87  88  89  90  91  92  93  94  95  96  97  98 
> 99 100
> >   99  99  99  99  99  99  99  99  99  98  99  99  99  99  99  99  99 
> 99  98
> >
> > It seems that the first and the last points are not linked. I have 
> choose a
> > value of d2 very high, and the distance between this two points is only
> > sqrt(162)
>
>I can't replicate this:
>
> > version
>          _
>platform i686-pc-linux-gnu
>arch     i686
>os       linux-gnu
>system   i686, linux-gnu
>status
>major    2
>minor    0.0
>year     2004
>month    10
>day      04
>language R
> > library(spdep)
> > spdep()
>[1] "spdep, version 0.2-22, 2004-08-07"
> > xy=expand.grid(1:10,1:10)
> > mydnn=dnearneigh(as.matrix(xy),d1=0,d2=50)
> > mydnn
>Neighbour list object:
>Number of regions: 100
>Number of nonzero links: 9900
>Percentage nonzero weights: 99
>Average number of links: 99
>
>The line "Number of nonzero links:" is calculated as:
>
> > sum(card(mydnn))
>[1] 9900
>
>You can also look at:
>
> > all(sapply(mydnn, length) == 99)
>[1] TRUE
> > which(sapply(mydnn, length) != 99)
>numeric(0)
>
>if you want to be sure it isn't card() getting it wrong. Puzzling. I don't
>think any of the relevant code has changed since September 2003.
>
>Roger
>
> >
> > Any ideas ?
> > Thanks
> > Stéphane DRAY
> > 
> -------------------------------------------------------------------------------------------------- 
>
> >
> > Département des Sciences Biologiques
> > Université de Montréal, C.P. 6128, succursale centre-ville
> > Montréal, Québec H3C 3J7, Canada
> >
> > Tel : (514) 343-6111 poste 1233         Fax : (514) 343-2293
> > E-mail : stephane.dray at umontreal.ca
> > 
> -------------------------------------------------------------------------------------------------- 
>
> >
> > 
> Web                                          http://www.steph280.freesurf.fr/
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at stat.math.ethz.ch
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >
>
>--
>Roger Bivand
>Economic Geography Section, Department of Economics, Norwegian School of
>Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
>Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
>e-mail: Roger.Bivand at nhh.no
>
>_______________________________________________
>R-sig-Geo mailing list
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Stéphane DRAY
-------------------------------------------------------------------------------------------------- 

Département des Sciences Biologiques
Université de Montréal, C.P. 6128, succursale centre-ville
Montréal, Québec H3C 3J7, Canada

Tel : (514) 343-6111 poste 1233         Fax : (514) 343-2293
E-mail : stephane.dray at umontreal.ca
-------------------------------------------------------------------------------------------------- 

Web                                          http://www.steph280.freesurf.fr/