* is_selected() returns if the current feature is selected
* num_selected() returns the number of selected features on the current layer
* is_selected(layer, feature) returns if the "feature" is selected. "feature"
must be on "layer".
* num_selected(layer) returns the number of selected features on "layer"
Adds the Viridis, Magma, Plasma and Inferno uniform color ramps
created by Stéfan van der Walt and Nathaniel Smith
See https://bids.github.io/colormap/ for more details
Note that I've thinned out the stops here, and only kept
every 5th stop from the original ramps
The Expression LIKE binary operator does not care about escape % and _ char.
No-one has already open an issue about it but in the OGC element PropertyIsLike the user can defined is own wild and single char. This mean that QGIS has to escape % and _ if they are not used as wild and single char.
Exposes simplification and smoothing algorithms to expression
engine, via:
- simplify(): applies Douglas-Peucker geometry simplification
- simplify_vw(): applies Visvalingam-Whyatt geometry simplification
- smooth(): smoothes a geometry
Carto tip: use smooth along with geometry generators to minimise
the typical "GIS" noded look of rendered geometries!
angle_at_vertex: returns average (bisector) angle to a geometry
at a specified vertex index
distance_to_vertex: returns distance along geometry to a specified
vertex index
line_interpolate_angle: calculates the angle parallel to a geometry
at the specified distance along the geometry
Sponsored by Andreas Neumann
This feature adds a 'collect' aggregation method resulting in a
single multipart geometry from a list of geometries. This is exposed
in the expression engine via the existing aggregate() function,
as well as a new collect() function.
Adds new functions
- line_interpolate_point: interpolates a point by a given distance
along a linestring geometry
- line_locate_point: returns the distance along a linestring to
the closest position on the linestring to a given point
Adds a new method to QgsGeometry for merging linestrings.
By passing a multilinestring, any connected lines will
be joined into single linestrings. Behind the scenes this
uses GEOS' line merge.
A corresponding expression function "line_merge" has also
been added.
This commit adds a number of different forms of aggregates to
the expression engine.
1. Aggregates within the current layer, eg sum("passengers")
Supports sub expressions (ie sum("passengers"/2) ), group by
( sum("passengers", group_by:="line_segment") ), and optional
filters ( sum("passengers", filter:= "station_class" > 3 ) )
2. Relational aggregates, which calculate an aggregate over
all matching child features from a relation, eg
relation_aggregate( 'my_relation', 'mean', "some_child_field" )
3. A summary aggregate function, for calculating aggregates
on other layers. Eg aggregate('rail_station_layer','sum',"passengers")
The summary aggregate function supports an optional filter,
making it possible to calculate things like:
aggregate('rail_stations','sum',"passengers",
intersects(@atlas_geometry, $geometry ) )
for calculating the total number of passengers for the stations
inside the current atlas feature
In all cases the calculations are cached inside the expression
context, so they only need to be calculated once for each
set of expression evaluations.
Sponsored by Kanton of Zug, Switzerland
This commit sets the framework for allowing expression functions to
use named parameters. Ie, instead of:
clamp(1,2,3)
you can use:
clamp( min:=1, value:=2, max:=3)
This also allows arguments to be switched, eg:
clamp( value:=2, max:=3, min:=1)
Additionally, it allows for a more structured definition of function
parameters to handle optional arguments and default values for
parameters. These are currently being done using a hacky infinite
argument list.
I've utilised the postgres ':=' syntax for specifying named arguments
to avoid potential collisions which may arise with the equality test
if we re-used just the '=' operator alone.
Sponsored by North Road
- add accessors: geometry_n, interior_ring_n
- add num_geometries, num_rings, num_interior_rings
- add nodes_to_points for converting every node in a geometry
to a multipoint geometry
- add segments_to_lines for converting every segment in a geometry
to a multiline geometry
nodes_to_points and segments_to_lines are intended for use with
geometry generator symbology, eg to allow use of m and z values
for nodes/lines with data defined symbology.
