On 14/09/13 21:01, Michael Barton wrote:
Moritz,
This is a nice addition.
Actually, not that nice. I just reread one of the papers you give as
reference [1] and it clearly states that the equation that you use for
estimating the expected mean nearest neighbor distance "cannot be used
for irregularly shaped study areas"...
Thanks, I'm really swamped right now. Do you want to add it to the script and
add your name to the authors?
I'll see what else I can find in the literature about how to calculate
the expected mean distance to see if having the actual study area
measures is really useful. If yes, I'll add the patch myself.
BTW, shouldn't the scripts v.nn.py and v.lda.py go into the addons svn ?
If you agree then I can add them there, with or without my patch. I've
also locally modified v.lda.py a bit to allow easier (to me at least)
use of the results.
Moritz
[1] http://www.geog.ucsb.edu/~dongmei/ppa/ppa.html
Michael Barton
School of Human Evolution&Social Change
Center for Social Dynamics& Complexity
Arizona State University
...Sent from my iPad
On Sep 14, 2013, at 9:11 AM, "Moritz Lennert"<[email protected]>
wrote:
Michael,
I've attached a patch to your very useful v.nn.py addon script. The patch
provides the following:
- a change of option names from input1,2 to 'from' and 'to'
- the possibility to provide a vector map with polygons giving the contours of
the study area for which to calculate the nearest neighbor coefficient - the
script just gets the total of all areas and all perimeters in the given map
- the possibility to provide numerical values for area and perimeter
Even though some people argue that the absolute value of the coefficient does
not mean much and that the exact size of the study area does not have an
influence on the relative values of the coefficient, I think it is a plus to
have the possibility to circumscribe the area. Especially since in its current
state the module gets the area and perimenter from the current region and as
this is a vector module most people won't even think about region settings.
(Running the module in the default n=1 s=0 w=0 e=1 region gives very weird
coefficient values.
Up to you to decide whether you want to add this into your script.
BTW: the script works perfectly in grass7 as well.
Moritz
<v.nn.py.diff>
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