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Carson Farmer (of manageR fame :-) this week submitted a patch for QGIS for evaluation. His patch adds three more class breaks strategies for graduated symbology in vector data: Pretty, Jenks (Natural Breaks) and StdDev. He explains the rationale behind this patch in his blog post here. I really like this new functionality (which should make its way into trunk soon). I made a couple of screen shots that will make it easier to visualise the different classifiers he has created:

What’s nice about the Jenks and Pretty breaks is that they create much more humanistic value ranges – it’s easier to identify with a value range of 6450000 – 11100000 than it is for something like 15394734.4297 – 20055646.2193

  • http://www.carto.net/neumann/ Andreas Neumann

    Hi Tim,

    It sounds like a great addition to QGIS.

    On the same topic – here is an idea for upcoming further improvements – the idea is not from me, but from the Atlas of Switzerland team.

    See http://www.atlasderschweiz.ch/ads2/english/functionality/analysis.html for an illustration.

    It would be nice if one had a histogram of the values and then see the class borders directly in the histogram. One could drag the borders and see the immediate effects in the histogram, meaning that the nr of elements left and right of the border change immediately. In addition one can click on one class in the histogram and set graphical styles, such as the fills.

    Something to consider for QGIS 2.0 ;-)

    • http://linfiniti.com Tim Sutton

      Yeah – I would also like to see a nice intuitive colour ramp editor make its way into QGIS – its functionality could be used in contexts like you describe above too. You suggestion would be a great addition too.

      Regards

      Tim

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  • Kurt

    Hi Tim,

    I now use the new version 1.6 but as far as I can see the new classification algorithms are not included??. Do I have download a special plugin??

    thanks

    Kurt

    • http://linfiniti.com Tim Sutton

      Hi

      They can be found in the ‘mode’ combo of the graduated symbol style (when using new symbology) for any vector layer.

      Regards

      Tim

  • maca21

    How I can display graduated symbol in KML file and show in GE? I am using QGIS but when I use OGR to convert SHP to KML it not showing the correct symbology that i use while making the SHP file..