Add statistics to the dissolve tool

[qgib]

Author Name: Giovanni Manghi (@gioman)
Original Redmine Issue: 6804

Redmine category:processing/qgis

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When dissolving there is a loss of information because features and their attributes are merged.

It makes sense to allow the user choose if in the resulting features he/she wants to have the attributes computed with some kind of statistics (each attribute with eventually a different stat).

Popular ones in other GIS packages are:

SUM
MEAN
MIN
MAX
RANGE
STD
COUNT
FIRST
LAST

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Related issue(s): #14314 (duplicates)
Redmine related issue(s): 4382

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[qgib]

Author Name: Giovanni Manghi (@gioman)

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see also #19756

[qgib]

Author Name: julie - (julie -)

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I don't know if it's relevant but I made a plugin which does just this, it's called "dissolve with stats". It's still experimental though.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Hi Julie,

I'm aware of your plugin, thanks for it, is indeed very useful. I would like to suggest to evaluate the possibility to add such stats functionalities to the core qgis dissolve plugin. This way the stats would be available directly in any qgis installation.

I'm personally developing a tool with many different geoprocessing operations, including dissolve with stats, but that will show in the "Processing" toolbox of QGIS. The tool uses pure Spatial SQL to do the geoprocessing.

[qgib]

Author Name: julie - (julie -)

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That would be great ! I'll wait for it.

[qgib]

Author Name: Bernhard Ströbl (Bernhard Ströbl)

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I included this issue in #21689, please consider closing this ticket if appropriate.

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Hi Bernhard,

I will add ogr/sql tools regardless of the work being done in native qgis tools, for several reasons: I like the flexibility of having GUI tools purely based on spatial SQL queries and because the tools already available have proven to be overall much quicker than the qgis/ftools counterparts. Cheers!

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• category_id was changed from 44 to Processing/QGIS

[qgib]

Author Name: Giovanni Manghi (@gioman)

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• easy_fix was configured as 0

[alexbruy]

GDAL version of the dissolve tool allows to calculate statistics.