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I have a point shapefile with several numeric fields, among them FuelFlow and Slope. I have successfully applied colour to the various points according to the value of the FuelFlow field. Now I would like to control some other attribute of the map symbols (shape? size?) according to the value in the Slope field. Something like slope between 0 and 10 gets one display style, 10-20 gets a second style, 20-30 etc.

I get the sense that this is possible in QGIS (using v 2.2.0 - Windows) according to some of the tools in the Style dialog, but I don't know where to start. Can someone point me in the right direction. I believe I saw one online posting about using a CASE statement in the style definition, but now 1) I can't find it in the UI and 2) I don't know how to construct the CASE statement.

Thanks

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I presume you want to achieve something like this:

enter image description here

You only need to define some rules, like bellow:

enter image description here

For the same results, you can use CASE statements, if you really want this:

enter image description here

This is my attribute table:

enter image description here

and the layer label:

enter image description here


EDIT:

If you want to specify the symbol and its color with data define values specified in the attribute's table, then your attribute's table may look like this:

enter image description here

Then, in the Rule properties, for each label, you need to choose SVG markerand to specify which fields stores the the SVG path and the symbol Color:

enter image description here

And here's the new result:

enter image description here

  • Close, but not quite. I want to independently define the symbology for two attributes. Using your example, I want to have the actual symbol (airplane, star, penta) linked to the content of the loc_field, and the colour of the symbol linked to the value in the slope field. Make sense? Newbie on this forum - how are you adding the screen shots? And I probably did not put this reply in the correct place; am I supposed to use the "answer your question" button? – user23742 Mar 1 '14 at 6:11
  • To add an image, you can use the 6th buton (counting from the left), when editing a question or an answer. (This isn't possible for a comment) – Sorin Călinică Mar 1 '14 at 6:35
  • @user23742 I've updated my response, to fulfil your requirements. – Sorin Călinică Mar 1 '14 at 14:08
  • I finally found how to use the graduated colours associated with one field plus a second field to control the size of the map symbol. Thanks for your help. – user23742 Mar 3 '14 at 15:36

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