Bug report #19099

Data defined Size legend is wrong when using separated symbols

Added by Harrissou Santanna about 1 year ago. Updated 9 months ago.

Status:Open
Priority:High
Assignee:-
Category:Map Legend
Affected QGIS version:3.4.1 Regression?:Yes
Operating System: Easy fix?:No
Pull Request or Patch supplied:No Resolution:
Crashes QGIS or corrupts data:No Copied to github as #:26929

Description

The data-defined size symbols feature has a set of unhandled issues i reported months ago (see list) but i think this one is a really broken feature that can lead to wrong information on maps.

Apply a scaled size to a point layer
At the bottom of the properties, choose to enable the data defined Size Legend
In the new dialog, choose "separated legend items", do the other settings and apply.
Most of the times, the symbols won't scale in the preview frame nor in the layers panel but the size displayed in the layers panel, hence in the layout legend, is really wrong. Really bigger than what's displayed in the map canvas.
If you switch to the "collapsed size symbols", you'll notice the difference of size and that sizes are coherent now.

Multivariate analisys.pdf (901 KB) Martina Savarese, 2018-10-21 09:51 AM

History

#1 Updated by Jürgen Fischer 11 months ago

  • Description updated (diff)

#2 Updated by Alexandre Neto 10 months ago

I have also noticed this problem. From some testing, seems that the symbols size in the legend is using the actual values on the data, and not the scaled values provided by the expression, for example.

coalesce(scale_exp("capacity", 0, 2717, 1, 10, 0.57), 0).

#3 Updated by Giovanni Manghi 10 months ago

  • Affected QGIS version changed from 3.1(master) to 3.3(master)

#4 Updated by Alexandre Neto 10 months ago

@gioman, can we consider this a regression. I mean, this used to work just fine before this several options to represent the legend were implemented.

#5 Updated by Giovanni Manghi 10 months ago

  • Priority changed from Normal to High
  • Regression? changed from No to Yes

#6 Updated by Martina Savarese 10 months ago

Think some of the other issues Harrissou linked are related to this problem. Attached file is a scheme of some test I have made, hope it can be some usefull

#7 Updated by Florent Monkerhey 9 months ago

I confirm that this problem is still present on QGis 4.3.1

#8 Updated by Giovanni Manghi 9 months ago

  • Affected QGIS version changed from 3.3(master) to 3.4.1

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