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I'm a new user trying to perform very simple operation but I'm completely stuck. I'd like to be able to select a number of features on the map and then get the sum of a particular field for only the selected features, on the fly. For example, summing the population fields for a number of counties that I've selected on the map. I don't need to store the sum in any way, I just need to quickly get it for reference.

  • That sounds like it would be a useful feature, but I don't think it exists in QGIS, at least not without writing code for it yourself. The fastest other way I can think of is to copy the selected features and paste into a spreadsheet. – csk Mar 23 '18 at 18:33
  • Actually, it looks like there is a way to do this, using the "show statistical" button on the attributes toolbar. I'll post this as an answer as soon as my computer stops being slow. – csk Mar 23 '18 at 18:39
  • Thank you. I think you're right. QGIS 3 has an "execute SQL" function that seemed promising, it looks like it isn't strictly for queries/selection as it can apply a SQL operation to only the selected features. But I'm using QGIS 2 for this project because there's way more information online. – Brett Sherwood Mar 23 '18 at 18:46
  • This is what I love about stack exchange. I didn't know this feature existed until I read this question and went looking for it. Now that I know it exists I'm sure I'll use the stats panel all the time. – csk Mar 23 '18 at 18:52
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The Statistics Panel displays various calculations based on a field.

  • To open the Statistics Panel, click the epsilon button in the Attributes toolbar.
  • Select the layer from the dropdown menu at the top of the stats panel.
  • Select the field from the dropdown menu below that.
  • At the bottom of the panel, check the box for "selected features only." Otherwise statistics are calculated for all features in the layer.
  • To choose what types of stats are calculated, use the "..." button at the bottom-right of the panel.

enter image description here

Screenshot is from QGIS 2.18. The stats panel also exists in QGIS 3.0.

  • Please use the check mark next to the answer to accept it. This way other people with the same question will know that this answer is correct. – csk Mar 23 '18 at 18:58

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