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I try to make a set of maps using QGIS Atlas. My maps will consist of selected feature with it's attributes (using $id = @atlas_featureid, and that's working). Basically - districts in particular city with population, from the lowest to highest. But I want also to show the previous shown features grayed out/in different color/etc. Like here GeoGIF.

I've found that the solution could be a formula $id <= @atlas_featureid. But it's not working properly in my case. The problem I've found is that ID of features in my project does not correspond to the order of features I want to show.

enter image description here

In my project - the order of maps generated with atlas is based on population value, from lowest to highest. How to handle this problem?

2 Answers 2

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I don't think $id has anything to do with the sort order of your districts. if you are sure of your features sort order first build a query in which you add an 'order' attribute (being the 'ranking' of your elements) that you will then use in the styling of your layer.

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  • Well, I've done it first. And I think that $id really does a difference here. On the picture above -the marked polygon has $id = 4. All the greyed out features has $id = 0, 1, 2, 3... I've checked it. I this case, since this feature is the first one (with order value = 1) it shall be the only feature selected...
    – muszynov
    Jan 20, 2018 at 9:59
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    weird ... i made several tests with different sort orders in the atlas generation. $id are 'static' (i mean : linked to a given feature) and never changed despite the change in the sort oder of the atlas ...
    – Snaileater
    Jan 20, 2018 at 10:15
  • Does the type of column on which the sorting is based makes a difference? I try to do many combinations but still, no progress!
    – muszynov
    Jan 20, 2018 at 10:21
  • weird you came to a case where $id were 0,1, 2, 3 ...
    – Snaileater
    Jan 20, 2018 at 10:34
  • But in QGIS feature $id starts with 0. $rownum starts with 1.
    – muszynov
    Jan 20, 2018 at 10:35
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I've found the answer. And the $id really makes a difference here. If You want to change the order of features basing on id, there is a MMQGIS plugin. Use "Modify" and "Sort" option to change the $id based on column chosen. Now it's working properly.

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  • would be nice to find a solution without that extra step of modifying and saving a copy of the original layer ...
    – Snaileater
    Jan 20, 2018 at 14:30
  • Well, it's problematic since the $id attribute is crucial for shapefile consistency. This solution doesn't take much time and often You only need 1-2 copies of original layer.
    – muszynov
    Jan 20, 2018 at 18:53

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