[Openspace] LISA used in Geoda and ArcInfo

[Roger Bivand]

On Tue, 13 May 2008, Patrick Yang wrote:

> Thank you Roger,
>
> I just find there is perhaps a bug in GeoDa. I caculated global Moran I
> manually as sugested by the GeoDa tutorial. The spatial lag value, based on
> Rook weight, are obviously problematic, not computed as the average of the
> neighbouring values. I am trying now to compare this by the data of Geoda
> samples.

Please wait until you are using shared data. I have posted:

http://spatial.nhh.no/R/etc/sids2a.zip

which contains a shapefile (the GeoDa distribution shapefile, with 4 extra 
fields: RR is the SID74/BIR74 raw rate, and the saved results from a 
univariate LISA using the enclosed contiguous county queen weights. I also 
include a short R script showing how the results match (they small 
difference is caused by GeoDa usin (n-1) in computing the sample variance, 
which is arguably better than localmoran() in spdep which just divides by 
n to agree with other work.

Try to get Arc to give you numeric results using this shapefile and these 
weights if you can. My Arc 9.1 toolbox is broken, and another list member 
tried but failed to get 9.2 to compute anything, so no working ArcGIS 
installations with working Local Moran Python scripts have come forward. 
Can anyone help? The most likely cause of the difference is that the Arc 
script does not generate the same weights, and the weights have to be the 
same to get the same answer.

Roger

>
> With best regards,
> Zhenshan
>
>
>
> On Tue, May 13, 2008 at 10:06 AM, Roger Bivand <Roger.Bivand at nhh.no> wrote:
>
>> On Mon, 12 May 2008, Patrick Yang wrote:
>>
>>  Dear Roger and other fellows,
>>> Thank you very much. In deed I think the results from Geoda are more
>>> reliable since it is original. But in terms of actual implications, I
>>> much
>>> believe the result of Arc Info. I attached the outcomes in graphics and
>>> also
>>> included my operation process for your reference. Hopefully you can help
>>> me.
>>>
>>
>> Patrick sent me his bulky Word document off-line, but unfortunately, it
>> did not contain anything helpful. I asked for screen shots not of the output
>> cartography, but of the actual input menus used to generate the results.
>> Sadly, neither of the software implementations is scripted, so no proper
>> history or journal is available (although all the argument values are shown
>> on the input forms, and also on Arc's Python report screen). So on Windows
>> Ctrl-Alt-PrintScreen of the input and report windows, please, or screen
>> capture to a paint program.
>>
>> What is needed is:
>>
>> The original data - shapefile as read into both Arc and GeoDa, indicating
>> which column is the problematic one;
>>
>> The GeoDa GAL file used (it can be read into Arc too, if need be);
>>
>> Screen shots of the input arguments as PNG files.
>>
>> It is impossible to debug software from output pictures - we have to know
>> what the input was.
>>
>> If your data are very private, use a sample data set from GeoDa, and try
>> to reproduce the problem. Your report of the Arc input includes "Euclidean
>> distance", which suggests that you may not have got the contiguity weights
>> you asked for, but rather inverse distance. I don't have access to Arc 9.2,
>> and 9.1 was known to be broken in some weighting settings, so we'll need
>> someone else to join in who has Arc 9.2 access.
>>
>> Roger
>>
>>
>>
>> I am much appreciated.
>>>
>>> The software version I used GeoDa 0.9.5-i5 (Aug 3, 2004) and Arc Info
>>> V9.2.
>>>
>>> Thank you,
>>> Zhenshan
>>>
>>>
>>>
>>> On Mon, May 12, 2008 at 8:04 PM, Roger Bivand <Roger.Bivand at nhh.no>
>>> wrote:
>>>
>>> On Mon, 12 May 2008, Patrick Yang wrote:
>>>>
>>>> Hello everybody,
>>>>
>>>>>
>>>>> Does any one have both experiences of computing LISA in Geoda and
>>>>> ArcInfo
>>>>> package of Spatial Statistic Tools. I ran the same set of areal data
>>>>> based
>>>>> on the same spatial weight matrix (the first order contiguity), but
>>>>> got
>>>>> very
>>>>> different outcomes:
>>>>>
>>>>>
>>>> Dear Patrick,
>>>>
>>>> In situations like this, it really helps to provide example data (for
>>>> instance a downloadable compressed archive file with the data files
>>>> and
>>>> screen shots of the two software systems showing the selected argument
>>>> values). I'm sure you have checked every possibility that this is not
>>>> a
>>>> difference in your use of the software, but a difference in the
>>>> software
>>>> itself, but more eyes seeing your situation may see something that you
>>>> have
>>>> not thought of.
>>>>
>>>> The key thing here is that the local Moran I values differ. This can
>>>> come
>>>> from three things: different data, different weights, and/or different
>>>> software implementations. As both implementations are widely used, the
>>>> community would benefit greatly if we could establish what is going
>>>> on. In
>>>> the Arc case, the Python code can be read if need be, but GeoDa local
>>>> Moran's I values typically agree with the R spdep localmoran()
>>>> function
>>>> output for the same data and weights. In other words, GeoDa is pretty
>>>> reliable, and indeed by the author of the original local Moran's I
>>>> paper.
>>>>
>>>> Can you provide a documented example showing the problem? Could you
>>>> also
>>>> please say which build of both implementation you are using - it may
>>>> be
>>>> something that has been fixed in a later release?
>>>>
>>>> Once the local Moran's I values agree, other differences will be
>>>> related
>>>> to how any testing is carried out, and here there is more room for
>>>> random
>>>> differences (different random number streams in GeoDa itself can give
>>>> slightly different results). So let's take this step by step.
>>>>
>>>> Hope this helps,
>>>>
>>>> Roger
>>>>
>>>>
>>>>
>>>> - most part of area are recoginized as low-low significally in Geoda,
>>>>> but as
>>>>> random process based on the Z-core (cut off by 1.96) in ArcInfo
>>>>> - There is no high-high combination in Geoda, but can find hot spots
>>>>> in
>>>>> ArcInfo
>>>>> - The caculated local Moran I is different in the two softwares
>>>>>
>>>>>
>>>>>
>>>>> Can anybody kindly help me to explain the reason? PS: I choose the
>>>>> standarized row for the weight matrix in ArcInfo but I guess in
>>>>> GeoDa it
>>>>> is
>>>>> the same configuration. if it is not so, please point it out. Any
>>>>> what
>>>>> other
>>>>> reasons? Thank you.
>>>>>
>>>>>
>>>>> Bests,
>>>>> Zhenshan
>>>>>
>>>>>
>>>>>
>>>>> --
>>>> Roger Bivand
>>>> Economic Geography Section, Department of Economics, Norwegian School
>>>> of
>>>> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
>>>> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
>>>> e-mail: Roger.Bivand at nhh.no
>>>>
>>>>
>>>>
>>>
>>>
>>>
>> --
>> Roger Bivand
>> Economic Geography Section, Department of Economics, Norwegian School of
>> Economics and Business Administration, Helleveien 30, N-5045 Bergen,
>> Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
>> e-mail: Roger.Bivand at nhh.no
>>
>>
>
>
>

-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no