[Qgis-user] Field Calculator/Python Plugins

[Alexandre Neto]

Hello Pretorius,

Both field calculator and Python calculator, allows one to calculate values
of columns, but does not affect the number of rows. What you need is to
somehow group (sum, mean, etc...) field values by a certain column common
value.

For that purpose I believe that Group Stats Plugin [1] is what you need.

Also If you are going to do lot of this kind of analysis, I would advice
you to put your data in Postgis or Spatialite so you can run SQL queries.

[1] http://plugins.qgis.org/plugins/GroupStats/

Hope this helped,

Alexandre Neto


On Thu, Oct 31, 2013 at 7:43 AM, Pretorius Deon - Lieutenant Colonel <
PretoriusDeon at saps.gov.za> wrote:

> Hi,****
>
> **1.       **Where can I learn more about on how to use the Field
> calculator as well as the Python Plugins as Iam new to this.****
>
> **2.       **I need to determine the unemployment rate for each
> district.  There are over 10 000 small_place_codes and just over 1000
> district. The majority of the small places overlaps with districts so I did
> an intersection for the two layers. An example of the results are as
> follows:****
>
> **3.       **How can I now calculate what the average percentage are per
> Small_Place_Code and also what the results will be for each district?****
>
> ** **
>
> Small_Place_Code****
>
> Districk_Name****
>
> Small_Place_Areakm2****
>
> District_AreaKM2****
>
> Unemployment_Rate%****
>
> *1112*
>
> *Hamilton*
>
> *0.0254*
>
> *2.1753*
>
> *6.21*
>
> 1113****
>
> Hamilton****
>
> 0.1254****
>
> 2.1753****
>
> 4.25****
>
> *1114*
>
> *Hamilton*
>
> *2.0245*
>
> *2.1753*
>
> *21.21*
>
> *1112*
>
> *Queens*
>
> *0.0045*
>
> *4.4316*
>
> *6.21*
>
> *1114*
>
> *Queens*
>
> *0.215*
>
> *4.4316*
>
> *21.21*
>
> 3333****
>
> Queens****
>
> 0.2121****
>
> 4.4316****
>
> 4.35****
>
> 3333****
>
> Queens****
>
> 4.000****
>
> 4.4316****
>
> 5.69****
>
> ** **
>
> Regards****
>
> Deon****
>
> ** **
>
> ** **
>
> ** **
>
> _______________________________________________
> Qgis-user mailing list
> Qgis-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-user/attachments/20131031/abcf9bfd/attachment.html>