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st: R: Moran I and spatial correleation help needed


From   "Carlo Lazzaro" <carlo.lazzaro@tin.it>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: R: Moran I and spatial correleation help needed
Date   Wed, 13 Feb 2008 18:44:31 +0100

Dear Recai,

quoting (and hoping to be right in quoting) a Scott Merryman's recent reply
to a similar thread:
...........................................................................
Maurizio Pisati has suite of commands for spatial data analysis that may be
useful.

See http://www.stata-press.com/journals/stbcontents/stb60.pdf

Scott
...........................................................................

Kind Regards,

Carlo
-----Messaggio originale-----
Da: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di RECAI AYDIN
Inviato: mercoledý 13 febbraio 2008 18.26
A: statalist@hsphsun2.harvard.edu
Oggetto: st: Moran I and spatial correleation help needed

Dear users,
 
I am new in "spatial correlation" and need your help. I appreciate if you
can help me. here are the commands I run and I have no problem getting the
output. However, I cannot say it for the output:)
 
  

spatcorr value, bands(0 1.5 3 4.5) xcoord(x) ycoord(y)cumulative

 

spatwmat, name(W) standardize xcoord(x) ycoord(y) band(0 1.5)eigenval(E)

  

spatreg value sf sf2 age lot br fb pool d1 d2 d3 d4 d5, weights(W)
eigenval(E) model(lag)

 

spatreg lnvalue sf sf2 age lot br fb pool d1 d2 d3 d4 d5, weights(W)
eigenval(E) model(error)

 

My questions are:

 

1) I noticed that I can use only one variable after "spatcorr" and I assume
it must be the dependent variable but that means the program is only
checking for the spatial correlation in that variable alone without knowing
what my full model is. That does not make sense to me. Then how does it
determine if the spatial correlation is "lag" type or "error" type unless it
defines the error as the deviation in Y?

 

2) I tried to run "spatcorr" with "lnvalue" as I normally use semi-log form
and I got different Moran I. Can I use this command with transformed
variable. How does that affect the interpretation of the I?

 

3) Is there any easy way of understanding if the spatial autocorrelation is
due to "lag" or "error" from the output?

 

4) When I have the output for the last two lines (spatreg) and compare them
with OLS, I do not see much difference even though Moran I, rho and lambda
all are significant. How can I  knoe that actually one is superior to the
others. This last one is especially important for me. Because I really doubt
about the importance of spatial autocorrelation and I need to be convinced
by one of the "believers":).

 

Thank you for your time and attention and I look forward to hearing from you
soon.

 

Recai  


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