<div dir="ltr">Now that's just gorgeous. <br><br><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Wed, Dec 4, 2013 at 7:13 PM, Nyall Dawson <span dir="ltr"><<a href="mailto:nyall.dawson@gmail.com" target="_blank">nyall.dawson@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I haven't had a chance to properly plan this out, but something which<br>
has been playing in the back of my mind is the idea of "table<br>
legends". Take a look at the legend in this map:<br>
<a href="http://www.cartogrammar.com/images/vba/cervical_cancer.jpg" target="_blank">http://www.cartogrammar.com/images/vba/cervical_cancer.jpg</a><br>
I'm thinking the user could specify the variable which is changed<br>
along each axis, along with the min/max value for that axis and number<br>
of rows/columns for the table. Then the classes would be generated<br>
automatically (maybe equal ranges? equal count? user specified?) and<br>
the symbol automatically generated for each cell in the table.<br>
<br>
The size and spacing of each cell could be user controlled, so that<br>
this type of legend would also work for symbol layers.<br>
<br>
As I said, I haven't really sat down to work out exactly how this<br>
would work yet... it's just a rough idea which I've been toying with!<br>
<span class="HOEnZb"><font color="#888888"><br>
Nyall<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
<br>
On 4 December 2013 22:34, Denis Rouzaud <<a href="mailto:denis.rouzaud@gmail.com">denis.rouzaud@gmail.com</a>> wrote:<br>
> Hi régis,<br>
><br>
> Martin Dobias will make a proposal soon for a legend refactoring.<br>
> You should see with him how to let those things happen in the future in the<br>
> new legend.<br>
><br>
> Cheers,<br>
><br>
> Denis<br>
><br>
><br>
><br>
> On 04. 12. 13 12:08, Régis Haubourg wrote:<br>
>><br>
>> Hi All,<br>
>> we have a long lasting problem with proportionnal legends in QGIS. It gets<br>
>> more problematic with V2, as those maps are so beautiful and popular.<br>
>><br>
>> I'm starting some brainstorming to clarify fonctionnal specifications what<br>
>> we actually want to have legends in layers registry and composer working.<br>
>><br>
>> Here are some exemples of what I would love to see in legends:<br>
>> - [0] proportionnal circles or square with 1 to 5 classes<br>
>> - [1] proportionnal symbols AND colors<br>
>><br>
>> Now that we have expressions everywhere, we probably will have to handle<br>
>> legends differently than in other GIS, where legend is generated once,<br>
>> when<br>
>> user tune symbology. Let me explain:<br>
>><br>
>> - user can now define expressions for size, color, rotation, border<br>
>> width...<br>
>> for any sub-marker (1 to n) of a symbol.<br>
>> - Moreover, we can use conditionnal expressions, and scale dependent<br>
>> conditions ($scale variable).<br>
>> - QGIS is also a server, we need to be able to generate legends working on<br>
>> really displayed datas.<br>
>><br>
>> Conclusion, It now is impossible to correctly pre-generate the legend by<br>
>> analysing symbology properties.<br>
>><br>
>> Does this sound possible to developpers to explore some other way? We<br>
>> could<br>
>> read real dataset to collect informations to build a legend, and<br>
>> eventually<br>
>> do some statistical classification to get discrete classes from continuous<br>
>> data?<br>
>><br>
>> We could do that on live or on-demand update maybe.<br>
>><br>
>> My idea was to collect rendered object in current canvas and current<br>
>> scale.<br>
>> BUT.. we can face discrete data - some kind of SELECT DISTINCT can do the<br>
>> trick - , OR continuous data - we need then to do some statistical<br>
>> classification to reduce the legend to 1 - 10 classes to get it readable.<br>
>> We also need some intelligence in those statistical classifications:<br>
>> - round values to keep it readable<br>
>> - display separate classes only if size or color distance is long enough<br>
>> so<br>
>> that human eye sees some difference on screen. ie: do not display for<br>
>> classes if symbol size varies from 0.5 to 0.7...<br>
>> - add some options in GUI to choose number of classes, type of legend<br>
>> rendering..<br>
>> - keep the classification process fast (subset of data with random<br>
>> sampling?)<br>
>> - test all use cases, I'm mostly thinking of points symbols, but lines<br>
>> and<br>
>> polygons must not be forgotten.<br>
>><br>
>> I'm sure plenty of scientists have already been theorizing all this. Any<br>
>> opinions? Could this be an idea for GSoC or other kind of training course?<br>
>><br>
>> I'll be pleased to get feedback from the community.<br>
>><br>
>> Cheers<br>
>> Régis<br>
>><br>
>> [0] <a href="http://kelsocartography.com/blog/?p=2224" target="_blank">http://kelsocartography.com/blog/?p=2224</a><br>
>> [1] <a href="http://www.geoclip.fr/img/bicol.jpg" target="_blank">http://www.geoclip.fr/img/bicol.jpg</a><br>
>><br>
>><br>
>><br>
>><br>
>><br>
>> --<br>
>> View this message in context:<br>
>> <a href="http://osgeo-org.1560.x6.nabble.com/Legend-for-proportionnal-symbols-and-expression-based-symbols-tp5092635.html" target="_blank">http://osgeo-org.1560.x6.nabble.com/Legend-for-proportionnal-symbols-and-expression-based-symbols-tp5092635.html</a><br>
>> Sent from the Quantum GIS - Developer mailing list archive at Nabble.com.<br>
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</div></div></blockquote></div><br></div>