[Numpy-discussion] Crosstabulation

sandric ionut sandricionut@yahoo....
Mon Jul 19 02:55:34 CDT 2010


Hi Friedrich:

For land-use a class would be for example forest, other would be orchard etc. 
For Slope gradient I would have values which <3 and between 3 and 7 etc. So, I 
will have 2 raster data with, let's say, 3 classes each: forest, orchards and 
built-up area and for slope gradient: 0-3, 3-15, 15-35. The cross-tabulation 
analysis should give me a table like:

            forest orchards built-up
0-3         10         20           15
3-15       5           10           20
15-35     5           15           15

where the numbers represents all the common cells, for example: 10 cells with 
forest correspond to 10 cells with 0-3 slope gradient interval and so on
(by cells I mean the pixel from a raster data)

The analysis is better illustrated here: 
http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=tabulate_area 


Ionut  



________________________________
From: Friedrich Romstedt <friedrichromstedt@gmail.com>
To: Discussion of Numerical Python <numpy-discussion@scipy.org>
Sent: Sun, July 18, 2010 12:09:04 AM
Subject: Re: [Numpy-discussion] Crosstabulation

2010/7/17 Robert Kern <robert.kern@gmail.com>:
> On Sat, Jul 17, 2010 at 13:11, Friedrich Romstedt
> <friedrichromstedt@gmail.com> wrote:
>> 2010/7/14 Ionut Sandric <sandricionut@yahoo.com>:
>> I'm afraid also Zach does not understand what you are talking about
>> ... So my first question (please bear with me) would be: What's a dem?
>
> Digital Elevation Map.
>
>>  (n/a in my dictionary)  And sorry for the cross-talk on the other
>> first post by you ...
>>
>> And by slope gradient you mean second derivative?
>
> No, the first derivative. "Slope gradient" is a reasonably common,
> albeit somewhat redundant, idiom meaning the gradient of an elevation
> map.

Thanks Robert, that clarifies a lot.

But still I don't understand how the crosstabulation shall work.  What
are the "classes"?

Friedrich
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