qgis – How to Dissolve Only Selected Features in a QGIS Layer

dissolveqgisqgis-processing

I am curious to know if it is possible to dissolve only the selected features in a layer in QGIS. In ArcGIS this is the default behaviour (which was actually someone annoying most of the time), but it can be useful to avoid having to export all the features to be dissolved to a new file, dissolving them, and then pasting them back into the original. Is this possible in QGIS? I do not see it in the Vector > Geoprocessing Tools > Dissolve dialog.

Best Answer

Select the features
Launch the Dissolve tool

It should as simple as that. No checkbox, the default behaviour is to use selected items, I think.

Related Solutions

Python Shapely – Dissolving Polygons to Single Part Features with Shapely and Fiona

I had an error due to the input shapefiles being a mixture of polygon and multipolygon types. I've included some code to skip the for loop for polygon types.

import fiona
from shapely import geometry
from shapely.geometry import shape, mapping

# open the original MultiPolygon file
with fiona.open('/home/matt/share/zoning/dissolve2.shp') as source:
    # create the new file: the driver and crs are the same
    # for the schema the geometry type is "Polygon" instead
    output_schema = dict(source.schema)  # make an independant copy
    output_schema['geometry'] = "Polygon"

    with fiona.open('/home/matt/share/zoning/output.shp', 'w',
                    driver=source.driver,
                    crs=source.crs,
                    schema=output_schema) as output:

        # read the input file
        for multi in source:

            polygon_shape = shape(multi['geometry'])

            if isinstance(polygon_shape, geometry.Polygon):

                # write the Polygon feature
                output.write({
                    'properties': multi['properties'],
                    'geometry': mapping(polygon_shape)
                })
            elif isinstance(polygon_shape, geometry.MultiPolygon):
                # extract each Polygon feature
                for poly in polygon_shape:

                    # write the Polygon feature
                    output.write({
                        'properties': multi['properties'],
                        'geometry': mapping(poly)
                    })
            else:
                raise ValueError('Unhandled geometry type: {}'.format(polygon_shape))

Best Answer

Related Solutions

Python Shapely – Dissolving Polygons to Single Part Features with Shapely and Fiona

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