[Qgis-user] Request for Guidance on Using 'Dissolve' Tool in QGIS with IUCN Data

[Ujaval Gandhi]

There is Vector Geometry --> Aggregate algorithm in the Processing Toolbox
that can summarize values while dissolving features. It can be a little tricky
to use so if you can't figure out how to use it - see my
tutorial https://www.qgistutorials.com/en/docs/3/areal_mean_rainfall.html
[https://mailtrack.io/trace/link/43bf6ee36d437ce2c50d26c89696b2046c0225b5?url=https%3A%2F%2Fwww.qgistutorials.com%2Fen%2Fdocs%2F3%2Fareal_mean_rainfall.html&userId=8747767&signature=d01c47db48ea788d]


Use Field Calculator for updating values using an expression, or just put the
layer in Edit mode, open the Attribute Table and update the values manually. 

---
Ujaval Gandhi
Spatial Thoughts
www.spatialthoughts.com
[https://mailtrack.io/trace/link/f80872d1a86e7c96a2818d9f373eff28606b2163?url=http%3A%2F%2Fwww.spatialthoughts.com&userId=8747767&signature=88087252a09861e6]




[data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=3D]
On Mon, Jun 26, 2023 at 11:33 AM Bernhard Ströbl via QGIS-User
<qgis-user at lists.osgeo.org> wrote:


> Hi Marcello,
> 
> you can choose which fields QGIS should use for the dissolve process. Only
> features that are homogeneous throughout the chosen fields will be dissolved
> into a new feature.
> Hope this helps
> Bernhard
> 
> 
> > Marcello Bilancioni via QGIS-User <qgis-user at lists.osgeo.org
> [qgis-user at lists.osgeo.org]> hat am 26.06.2023 01:54 CEST geschrieben:
> >
> > 
> > Good morning,
> >
> > I am currently working with the mammal species distribution data provided
> > by IUCN, and analyzing these shape files in QGIS.
> >
> > As part of my analysis, I have been using the 'Dissolve' tool in QGIS to
> > merge rows of the same species into a single entry. This operation is aimed
> > at creating a single comprehensive polygon that represents each species'
> > entire distribution range. However, while the tool successfully
> > consolidates the geometries, it looses important attribute data from the
> > original attribute table. In particular, this leads to the loss of valuable
> > information within the "Presence" and "Origin" columns, where the values
> > can differ across entries for the same species.
> >
> > Could you provide any recommendations on how to avoid such data loss? Is
> > there a strategy or method that could effectively summarize or retain this
> > varied information while processing the data using the 'Dissolve' tool?
> >
> > Furthermore, in my dataset, I have noticed some specific values under the
> > "Presence" and "Origin" columns: "presence 3", "presence 6", and "origin 5"
> > (I have attached a list with those species here). According to the IUCN
> > guidelines, these values need to be updated or adjusted. Do you happen to
> > know how to update these entries within QGIS best?
> >
> > Thank you in advance for any assistance you can provide.
> >
> > Best regards,
> >
> > Marcello Bilancioni
> > _______________________________________________
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