Finding mean and stdDev of vector layer field using PyQGIS

Asked Sep 23 '21 at 02:50

Active Sep 23 '21 at 02:55

Viewed 30 times

I am going to standardized a vector layer field in Python console in QGIS, for that I want to get mean value and stdev value of the field.

How do I find mean and stdev in using PyQGIS.

I tried this. It is not working

layer=iface.activeLayer()
idx=layer.fields().indexFromName("mean")
ave = layer.meanValue(idx)
print (ave)
stdDev = layer.stdDevValue(idx)
print (stdDev)

edited Sep 23 '21 at 02:55

PolyGeo

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asked Sep 23 '21 at 02:50

Chathu_T

1

See my answer to Summing values in one field using PyQGIS. In your case you'd need to use QgsAggregateCalculator.mean and QgsAggregateCalculator.StDev respectively. If that works for you, I'll close this question as a duplicate. – Germán Carrillo Sep 23 '21 at 03:49
Thank you for the solution. But I am getting this error attributeError: type object 'QgsAggregateCalculator' has no attribute 'mean' – Chathu_T Sep 23 '21 at 04:58
1

Should be QgsAggregateCalculator.Mean (with a capital M). – Ben W Sep 23 '21 at 05:04
Thank you so much I got it. This is working. – Chathu_T Sep 23 '21 at 05:10
2

@Chathu_T, glad you got it working. FYI all Qgis api classes and methods are documented. It is a very good habit to adopt to consult the documentation e.g. https://qgis.org/api/classQgsAggregateCalculator.html#a51eb9f5752cf107d72266829a21cf2fa – Ben W Sep 23 '21 at 05:12
Nice, @Chathu_T. Since this answer works for you, don't forget to upvote it. – Germán Carrillo Sep 23 '21 at 11:05

Finding mean and stdDev of vector layer field using PyQGIS

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