[Qgis-user] Scale based label rendering

[Andreas Neumann]

Hi Ross,

I sucessfully use $scale - it should just work, otherwise it is a bug 
either in your statement or in QGIS.

I guess in your example your statement is wrong as AND/OR can only be 
combined with boolean values (true/false). In your case you combine a 
number with another number with OR and of course your statement fails.

You could write your statement with nested CASE statements, such as:

CASE WHEN type = 'town' THEN
     CASE WHEN $scale < 100000 THEN 15 ELSE 10 END
   WHEN type = 'city' THEN
     CASE WHEN $scale < 100000 THEN 20 ELSE 15 END
END

You should get a warning if the syntax in your statement is not correct.

Andreas


Am 2013-11-06 17:44, schrieb McDonaldR:
> Thanks Bernhard
> 
> That does work.
> 
> Any idea how the $scale function works then?  It is supposed to return
> the current scale of the map canvas but is only available in some
> contexts and will be 0 otherwise.
> 
> Ross
> 
> -----Original Message-----
> From: qgis-user-bounces at lists.osgeo.org
> [mailto:qgis-user-bounces at lists.osgeo.org] On Behalf Of Bernhard
> Ströbl
> Sent: 06 November 2013 16:02
> To: qgis-user at lists.osgeo.org
> Subject: Re: [Qgis-user] Scale based label rendering
> 
> Hi,
> 
> not a solution but a workaround:
> simply copy the layer and define a different visibility scale range.
> 
> Bernhard
> 
> Am 06.11.2013 16:54, schrieb McDonaldR:
>> Hello list
>> 
>> I want to vary the size of my labels on features both by attribute and 
>> map scale.  So, for example, I have a layer of towns and villages and 
>> I want towns labelled with a font size of 20 and villages with a font 
>> size of 10.  I can do this with in the label size expression builder:
>> 
>> CASE WHEN "type" = 'town' THEN 20 ELSE 10 END
>> 
>> Now, how can I vary the label size with scale?  When the scale is 
>> smaller than 1:100000 then towns must be size 15 and villages size 8.  
>> I thought something like this would work:
>> 
>> (CASE WHEN "type" = 'town' AND $scale<  100000 THEN 20 ELSE 10 END) OR 
>> (CASE WHEN "type" = 'town' AND $scale>  100000 THEN 15 ELSE 8 END)
>> 
>> I tried with the $scale function under Record category but then the 
>> labels disappeared.
>> 
>> Any suggestions?
>> 
>> I am using QGIS 2.0.1-3 on Windows 7.
>> 
>> Thanks
>> 
>> Ross
>> 
>> Ross McDonald | GIS Data Coordinator | Resources Department, IT 
>> Division | Angus Council, Angus House, Orchardbank Business Park, 
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