Hi
Neither GeometryGenerators nor Vector Field Markers work on tables
without geometry, unfortunately. You didn't inform us, that you don't
have geometry in your table.
You can, however, create a "Virtual Layer" and write some SQL to create
a geometry from your attributes: menu "Layer" --> "Create Layer" -->
"New Virtual Layer" - where you can use your existing tables and create
a new geometry column with SQL. See
https://docs.qgis.org/testing/en/docs/user_manual/managing_data_source/create_layers.html#creating-virtual-layers
Or, if your table is a CSV file, then you can assign attribute columns
to a point geometry and then just hide the point rendering if you don't
need it.
This is an unfortunate limitation of QGIS, that there is no "easy" way
to add a geometry column to table that doesn't have geometry (or if it
is possible, then I don't know it).
Hope this helps you,
Andreas
Am 13.11.20 um 14:52 schrieb L.W.:
Does it works on Layers with no geometry?
My layers do not have a geometry.
Am 13.11.2020 um 11:56 schrieb Andreas Neumann:
Yes, you need point data to start from, but then vectors can bei/are
generated from the attributes you mentioned.
Andreas
Am 13.11.20 um 11:47 schrieb L.W.:
from the docs ...
****It can only be used to render point data****
12.2.2.2.6.The Vector Field Marker
<https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#id15>
The vector field marker is used to display vector field data such as
earth deformation, tidal flows, and the like. It displays the
vectors as lines (preferably arrows) that are scaled and oriented
according to selected attributes of data points. ****It can only be
used to render point data****; line and polygon layers are not drawn
by this symbology.
The vector field is defined by attributes in the data, which can
represent the field either by:
*
*cartesian*components (|x|and|y|components of the field)
*
or*polar*coordinates: in this case, attributes
define|Length|and|Angle|. The angle may be measured either
clockwise from north, or Counterclockwise from east, and may be
either in degrees or radians.
*
or as*height only*data, which displays a vertical arrow scaled
using an attribute of the data. This is appropriate for
displaying the vertical component of deformation, for example.
The magnitude of field
Am 13.11.2020 um 11:34 schrieb Andreas Neumann:
Or even easier: use the "Vector Field Marker":
https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?#the-vector-field-marker
Am 13.11.20 um 11:33 schrieb Andreas Neumann:
Hi,
Yes - you can use Geometry Generators for that. Use the
make_point() and make_line() expressions for that.
See
https://docs.qgis.org/3.10/en/docs/user_manual/style_library/symbol_selector.html?highlight=geometry%20generator#the-geometry-generator
Greetings,
Andreas
Am 13.11.20 um 11:26 schrieb L.W.:
Hi,
is it possible to draw automatically a line between two points
defined
by 4 fields (x1,y1 - x2,y2) in an attributetable?
but I do not want to add a line-layer based on this table nor
want to
draw the line by hand.
thanks
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