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How to make a memory vector layer in QGIS permanent?
You can also make a memory layer permanent (to any format) by using the save as tool. The current QGIS version currently in development (2.7 master) has integrated the memory layer plugin in it’s core functions, but with a different name, Scratch layers.
How can I duplicate a layer in QGIS?
While it’s very handy to be able to copy and paste the layer style in 1.8+, it would be nice to be able to select a layer and right-click to copy or duplicate it directly. Any easy way of doing this, like a Python command? Update: @dakcarto’s suggestion works perfectly.
How can I save a vector layer to memory?
Use it in further geoprocessing, save it’s definition to .qlr and reuse it in other projects. on DB level, simply save your queries as Views and load them into QGIS. Again, as above, you can view (no kidding) the results of queries just as with other layers, and use its ‘data’ in further geoprocessing, save to file or whatever.
How is a geometry class represented in QGIS?
In QGIS they are represented with the QgsGeometry class. Sometimes one geometry is actually a collection of simple (single-part) geometries. Such a geometry is called a multi-part geometry. If it contains just one type of simple geometry, we call it multi-point, multi-linestring or multi-polygon.
How does QGIS copy and paste line features?
Copy a line feature and paste it in a polygon layer: QGIS pastes in the target layer a polygon whose boundary corresponds to the closed geometry of the line feature. This is a quick way to generate different geometries of the same data.
What kind of operations can be done in QGIS?
QGIS uses GEOS library for advanced geometry operations such as geometry predicates ( contains (), intersects (), …) and set operations ( combine (), difference (), …). It can also compute geometric properties of geometries, such as area (in the case of polygons) or lengths (for polygons and lines).