[Openspace] LISA used in Geoda and ArcInfo

[Roger Bivand]

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