I would need to reproduce an ArcMap cartography project in an equivalent QGIS project. in the ArcMap version the symbolization of some layers is done through the "Unique values, many fields" method, ie: enter image description here

enter image description here

how can i "translate" this method in QGIS?

  • The method is called "rule based" styling in QGIS. You should find several questions and answers to this topic here as well as some basics in the QGIS user guide. It is possible to use SQL-rules or to "refine" existing rules. With "refine" you can add your subcategories similar to ArcMap. – Matte Jul 2 '18 at 14:06
  • Sorry but I could not find any examples of expression about "Unique values, many fields". Could someone help me to understand how to build a correct expression? – Andrew-63 Jul 2 '18 at 15:03

Select the Categorized type in the layer styling dialog then click on the ''ε'' symbol at the right of the column drop-down selector then you could construct an expression to concatenate as many field as you want for unique value symbology.

For three field you would use :"Field 1" || "Field 2" || "Field 3"

The ''||'' symbol concatenate the field together, for better readability of your different categories you could insert a space between the field ("Field 1" || ' ' || "Field 2" || ' ' || "Field 3") (edit : Arcgis use a '', '' as a separator)

After validating your expression just click the Classify button...

  • Sorry but I did not understand how it should work, what would be the result of the classifying? – Andrew-63 Jul 2 '18 at 15:24
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    @Andrew-63 it should be a unique set of the combinations you concatenated in the solution above - don't think about this as 'how does ArcGIS do it', think about what you are doing with your data as it applies to your map - combining multiple fields into combinations of classes, then assigning symbols to those classes. The above solution should work for you. – DPSSpatial Jul 2 '18 at 15:44
  • This will create value that are the 'addition' (concatenation) of the 3 field, the classifying would attribute a class for each (unique) new value. Also looking at the picture of your arcgis symbology it seem that some of the categories have been merged together so what you are trying to do is not strictly unique value... – J.R Jul 2 '18 at 15:54
  • Sorry, do you mean that the classification will provide as many classes as all the possible combinations of values for the three selected fields and after should I then assign a style for each class? Will this also result in combinations of values that do not match those used in ArcMap? – Andrew-63 Jul 2 '18 at 16:21
  • Yes,you will get as many classes as all the existing combinations of values for the three selected fields. In arc map you can merge several different classe before applying symbology but I don't think you could do that in qgis so you may have to set the same symbology to several different classes to get the same result. If you have an easy way to define your class it may be easier to use rule based symbology – J.R Jul 2 '18 at 16:32

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