forum.vdsworld.com

[Capinha]

Hello there,

I'm developing a software application that interacts with GIS (geog. information systems) software trough DDE.
In this kind of applications there is a lot of need for retrieving statistical parameters from usually large lists (arrays) like mean, max, Std...
I'm doing this on the GIS software and then import it to vds application but its somewhat "clumsy".

Does any one knows a way of working with large lists, arrays and calculate statistical values... using VDS? Like an extension dll, api calls, free DDE software...

Cheers

César Capinha


www.cesarcapinha.com
capinha.weebly.com

[Aslan]

1. Can you provide a more detailed example of what you're trying to do with the list?

2. Exaclty what is the criteria your statistics require?

3. Can you provide a good sample list of what you retrieve from GIS?

[Capinha]

Well, mainly what I retrieve from GIS software is Lists with floating point like this:
1.3
4.7
33.5
15.6
12.1
75.2
2.7
22.1
13.6
...
I would like to reach a simple way to achieve the maximum and minimum value present in the list, its average value, well and if possible any others like the sum, standard deviation, variance...

I'm using Ilwis GIS Open 3.4 an open source (http://52north.org/index.php?option=com_projects&task=showProject&id=30&Itemid=127) it really works great with VDS using DDE, very easy to use.
Using it I can almost create any of this calculations and retrieve its value, but for each calculation this software creates a output column. It would be desirable to do this outside the GIS.

I'm searching for some software that can do this using DDE or command line like interface... Does MySQL allow any of this calculations (I don't think so, but never used it...) Maybe an external library...

I really really like vds but I think that an extra power in math functions and the ability to work with number lists would take it to a new much wider level.

[Aslan]

You can certainly get min, max, avg, and sum with VDS.
If you place the GIS values in a sorted list (or place them in a table and use the "LIST SORT" command) you can get the min and max which would be the first and last item respectfully. Just add the values in a REPEAT loop to get the sum and then divide by the total number of items ( @COUNT() ) to get the average.

Forgive me but I don't know the equations for 'standard deviation' and 'variance'. VDS has a lot foating point math functions that may help.

As far as SQL extentions, there is a free DLL already that interfaces with MySQL and there is also a database DLL that uses ODBC that I use extensively with MS SQL. Tommy Sools is the author of both. If you can deal with the language barrier, MidisaSoft (New owner) also has a (not freeware) VDS ODBC extention with quite a few advance features.

Hope this helps

[Capinha]

It really helps, it gave me a new way of seeing the problem (and possible solutions).

Table dialog element, how about that...

The more I use this language the more I like it...

Very Gratefull

César Capinha