Feature request #960
Area scale field: make standardized symbol dimension and legend
|Pull Request or Patch supplied:||Resolution:||wontfix|
|Easy fix?:||No||Copied to github as #:||11019|
I find the "Area scale field" an important enhancement from QGis 0.9.2, but two enhancements should be
1 - make the symbol dimensions appear "standardized", and not directly proportional to the attribute values. The problem raises when we have big values, and the symbols appear to large, even if one reduces the dimension to the minimum (size 3).
2 - make appear the symbol classes in the legend, otherwise we loose the visual usefullness of having graduated symbols.
#2 Updated by Giovanni Allegri about 12 years ago
I'm referring to the symbology option for punctual features, that lets you choose a single layer whose dimension (and rotation) may be controlled by means of a selected attribute.
You can choose a not better defined "dimension" factor that applies to the symbols size proportionally to the attribute value. Now, if you have huge values you can get enormous balloons even if you set the minimum "dimension" (by default the lower limit is 3).
I think it could be better to stanrdardize the dimensions of the symbols on the basis of a minimum-maximum value.
In this way the user could choose the best visualization it needs.
In formula it could be:
(attribute_value - min_dimension)/(max_dimension-min_dimension)
or something similar...
#3 Updated by Magnus Homann almost 12 years ago
- Status changed from Open to Closed
- Resolution set to wontfix
I'm not so sure this is a good idea. The question then arise, what kind of expressions should we allow? Scale based on a generic forumla on 1 or more fields?
No, I propose that should be up to the layer to proivde the correct values.
#4 Updated by Giovanni Allegri almost 12 years ago
- Resolution deleted (
- Status changed from Closed to Feedback
Ok, you can advocate my suggestion, but the problem remains: these days I'm working on a layer, and I need to make graduated symbols on the base of a floating attribute. The values are so high that the balls cover the entire screen. Should I create an attribute field with scaled values?!
Maybe I miss something from the new Qgis versions... How would you deal with this?
Anyway, before closing a ticket it would be nice to propose a solution...
#7 Updated by Giovanni Allegri almost 12 years ago
Sorry, there were problem pasting the text
*Ok, I leave this ticket, but I haven't seen any GIS needing that. I usually select the bins/classes, max-min values, and classification method (linear, quantiles, etc.), and that's all... I can't uderstand why it cannot be done for symbol dimensions.
Maybe I can't expain what I mean...Anyway, don't mind.
#9 Updated by Giovanni Allegri almost 12 years ago
#12 Updated by Jean-Roc Morreale over 10 years ago
Biased proportional symbol are possible in most GIS software, here a few methods :
Some good read on the subject :
/ Perceptual Scaling of Map Symbols
Daniel R. Montello, Cognitive Map-Design Research in the 20th Century: Theoretical and Empirical Approaches / PDF
James Flannery, The Graduated Circle: A Description, Analysis, and Evaluation of a Quantitative Map Symbol
Susumu Tanimura and al., Proportional Symbol Mapping in R / PDF
Original / post on qgis-dev's ml
Making it possible to show the size in the legend would be a small step that would still be compliant with Tufte's rigorous ideas.