[Qgis-user] FW: Using one vector layers to calculate the unemplyment rate in another vector layer

[Zirneklitis]

Sorry, you have to do it from the beginning as the area of The Census 
sub-place should be calculated as well.

The 4th step is something like:


                         area_of_intersection
number_of_unemployed * ----------------------------
                         area_of__The_Sensus_sub-place


Afterwards: Vector / Data Management Tool / Join attributes by location.

Remember to check "Take summary of intersecting features".

K.


Pretorius Deon - Lieutenant Colonel wrote:
> Hi
>
> 1.      Thanks for the assistance.  I have done that up until your 3de explanation point.
> 2.      All the Sensus Sub Place data are now "cut" and within each policing district. Perhaps any assistance on how I can now get the averages of each of the Sub Place "numbers" per policing district.
>
> Regards
> Deon
> -----Original Message-----
..
> Just an idea:
>
> 1. Using the Field calculator add a new column with polygon areas for the police district  layer.
>
> 2. Create the third layer as an intersection between the Sensus sub-place layer and the  police district  layer.
>
> 3. Using the Field calculator add a new column with polygon areas. Now you have a attribute table to calculate the statistics.
>
..
> Pretorius Deon - Lieutenant Colonel wrote:
>> ..
>> I have a vector layer that exist out of about 1000 polygons of the
>> different police districts.  Then I have a Sensus sub-place vector layer
>> with over 10 000 sub-places which indicate the number of unemployed
>> citizens per polygon.  The Sensus sub-place layer therefor overlaps with
>> the police districts and when visualize some sub-places can make up 1%
>>    up to 100% of a given police district.  Most of the police districts
>> also  contains 4 or more sub-places.  The problem is  I want to
>> calculate the "approximate" unemployment rate per police district by
>> using the data from the Sensus sub-place layer.  Is there perhaps an
>> explanation on how I can determine" approximately proportionally" what
>> the unemployment is per police district.   I am new to QGIS and not up
>> to date with programming, however any assistance would be appreciated.
>> ..