[Qgis-user] Select data from a specific layer

[Ujaval Gandhi]

get_feature() will get you the feature.Your current expression will get you
the first feature from 'V_TB_ATTIVITA_PT_NR' layer where the "Colore" value
is 'N'. - I don't think that is what you want.  You need to query for a
feature from another layer that relates to the current feature, (using a
common field value).  Once you get the feature, you can use the
attributes(feature)['Colore'] to read the "Colore' field from that feature.

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Ujaval Gandhi
Spatial Thoughts
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On Tue, May 18, 2021 at 4:35 AM Delaz J <delazj at gmail.com> wrote:

> Hi Dario,
>
> Could you try with 'Colore' and not "Colore" (pay attention to the simple
> vs double quotes)?
>
> Regards,
>
> Harrissou
> Le 18/05/2021 à 00:41, Dario C a écrit :
>
>   Hi, thank you for your reply, but I still don't understand how to do...
> sorry
>
> i tried to write this code in colour expression, but I don't understand
> what "value" is in get_feature :
>
> CASE
> When
> get_feature('V_TB_ATTIVITA_PT_NR',"Colore",'N')='N' then color_rgb (0,0,0)
> When
> get_feature('V_TB_ATTIVITA_PT_NR',"Colore",'R')='R' then color_rgb
> (255,0,0)
> END
>
> Consider that I have a virtual field called "Colore" where I have 'N' or
> 'R' in case it is black or red color.
>
> Thank you for your kind availability.
>
> cheers
>
> Il giorno lun 17 mag 2021 alle ore 09:09 Ujaval Gandhi <
> ujaval at spatialthoughts.com> ha scritto:
>
>> You can select the layer under 'Plot Parameters' and its attributes will
>> be available in the expression. (see attached screenshot).
>>
>> If you need to get the attribute from another layer, you can use the
>> get_feature() function to get feature from another layer by specifying the
>> layer name.
>> [image: Logo] <https://spatialthoughts.com/>
>> Ujaval Gandhi
>> Spatial Thoughts
>> mobile: +91-8095684687
>> email: ujaval at spatialthoughts.com
>> [image: LinkedIn icon] <https://www.linkedin.com/in/spatialthoughts/>  [image:
>> Twitter icon] <https://twitter.com/spatialthoughts>
>>
>>
>>
>>
>> On Mon, May 17, 2021 at 2:47 AM Dario <dario955i at gmail.com> wrote:
>>
>>> Hi,
>>>
>>> I should get some data from a specific field of a specific layer but I’m
>>> stuck.
>>>
>>> I’m using “Data Ploty” plug-in and I’d like to customise the colour of
>>> the chart using expression.
>>> As I’m working on layout I can’t see any field into expression menu, so
>>> I need to call a specific layer and then the field.
>>> I’d like to write something like that but, of course, selecting the
>>> correct layer:
>>>
>>> CASE
>>> WHEN "Civici" = 'Neri' THEN color_rgb(0,0,0)
>>> ELSE color_rgb (255,0,0)
>>> END
>>>
>>>
>>> Thank you in advance.
>>>
>>> Cheers
>>>
>>> _
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>>
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