[Qgis-user] How to shorten this in Field Calculator

[Wouter Impens]

Hi Willem,

You could calculate this using a python script.

If you like, I could send you some code examples how to make a new field,
use expressions, etc. in python.


Greetings
Wouter Impens

Op wo 28 aug. 2019 om 13:58 schreef Willem Korevaar <wereldvak at gmail.com>:

> I would like to shorten the following proces (= workaround)  of
> calculating a simple  Rs (Spearman Rank correlation) in the Field
> Calculator .
>
> https://drive.google.com/file/d/1vuW50nm1h4LduaAO01ThO6Nv-VXUGBo9/view?usp=sharing
>
> [image: image.png]
> and as an example:
>
> [image: image.png]
>
> Its about two columnsin the table  (X-Y in the example )  : P_00_14_JR
> (age 0-14 in %) and  P-N_W_AL (people from outside W-Europe in %).
> I know that it can be done with an R- script, but as I m working with
> students and I want to show them how the formula works and R is not working
> anymore on the schoolsystem I tried a workaround. It works, but there are
> too many steps.
> My workaround is in 2.18.9 :
>
>
>    1. using the plugin Sort and number and ranking both columns. So two
>    more fields : r_014 and r_nw (rang x and y)
>    2. make kolom 6 ((x-y)2) using Field Calculator:
>    (  "r_0-14"   - "r_nw_ll"   ) ^ 2
>    3. create new field in FC named RS:
>    1- (  ( 6 * (  sum( "kolom6"  ) ) / ( ( (count(  "BU_NAAM" ) ^ 2) * (
>    count(  "BU_NAAM" ) ) ) - count( "BU_NAAM"  ) ) ) )
>    In which 'BU_NAAM' = n (number of objects in this case names of
>    neighbourhoods in Den Haag) but this one can be any other fieldname.
>    New fieldname = RS and with 'Real' and precision 5
>    4. in this case Rs = 0,488 which means a little correlation
>    (I know that there should be no ties in the values, but that would
>    make the proces more complicated in case of
>
> Is there a way in the FC I can do it in less steps?
> This is the link to the table used in QGIS and the Rs formula in the
> example:
>
> https://drive.google.com/file/d/1vuW50nm1h4LduaAO01ThO6Nv-VXUGBo9/view?usp=sharing
> I hope this all wil make sense :-)
>
>
> Gr
> Willem Korevaar
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