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Results tagged with expression
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user 99589
Expressions are SQL-like statements that are used to evaluate dynamic properties.
15
votes
4
answers
3k
views
Difference between quotation marks ('single' vs "double") in QGIS
For instance, if I type something in the Expression dialogue I will have a different output.
"something", it is written as
The Output is NULL. …
- 141
2
votes
Calculating field using expression taken from DataFrame with PyQGIS
following methods startEditing() and commitChanges() and of the QgsVectorLayer class:
layer.startEditing()
...
layer.commitChanges()
There are also several suggestions regarding your code:
check your expression … expression = QgsExpression(row['calcul'])
# checking if expression is valid
if expression.isValid():
# looping through …
- 34k
3
votes
Accepted
Display point with heighest value in group of points
Perhaps, you will find this expression suitable for you:
geometry_n(
collect(
expression:=$geometry,
group_by:=substr("NumeroNom", 0, 5),
filter:="AmslFt"=maximum("AmslFt", …
- 34k
3
votes
Accepted
Recreating the shape of curved arrows with QGIS Geometry Generator
Unfortunately, it is not a desirable Geometry Generator, however, I can suggest a PyQGIS approach. It is primarily based on the segmentizeArc() method of the QgsGeometryUtils class. Perhaps this tool …
- 34k
2
votes
Getting lat/long for centroids using QGIS
A possible solution using PyQGIS.
An Extension to the answer provided in this thread Adding x,y coordinates to Attribute table in QGIS. The above solution is primarily based on the QgsCoordinateTransf …
- 34k
3
votes
QGIS expression: when using overlay_nearest sometimes a feature considers itself its nearest...
Therefore, like in this thread Drawing 10 nearest lines from each point connecting to the centroid of the 5 points nearest to each point with QGIS expression, I am simply suggesting to delete it by its … However, in such a case, the number in limit should be incremented in one more feature.
array_remove_at(
overlay_nearest(
layer:=@layer,
expression:=fid,
filter:=letter='A' …
- 34k
5
votes
Filtering maximum and minimum length in QGIS Attribute table
The logical operator should be OR instead of AND.
"Length" < 50 OR "Length" > 100
See Logical connective for more details.
Another solution will employ NOT BETWEEN operator:
"Length" NOT BETWEEN 50 A …
- 34k
9
votes
Expression to replace characters in QGIS Attribute table
You may also try the following expression:
array_to_string(
array_foreach(
string_to_array("test"),
if(
to_int(@element)>0,
@element||'F',
abs(@element …
- 34k
2
votes
Expression for assigning ID by grouping and ordering polygons in QGIS
Inspired by @GabrielDeLuca's answer:
array_find(
array_reverse(
array_agg(
"id",
group_by:="Group",
order_by:="area"
)
),
"id"
…
- 34k
1
vote
Calculating interior angles of polygons or lines in QGIS
Currently working only for Single Part Polygons.
There is "LF Tools " Plugin, that possesses the "Calculate polygon angles" tool for that.
This algorithm calculates the inner and outer angles of th …
- 34k
3
votes
Adding new field in point layer with attribute from another layer in QGIS
Currently a bit "old-fashioned" approach using the aggregate() function:
aggregate(
layer:='polygon_layer',
aggregate:='concatenate',
concatenator:=',',
expression:=to_string("id"), …
- 34k
3
votes
Identifying neighbouring polygons but field calculator preview and output are different
overlay_intersects(@layer, "id")))
2. aggregate()
As was mentioned by @J.Monticolo in his comment, one can use a small buffer around $geometry.
aggregate(
layer:=@layer,
aggregate:='concatenate',
expression …
- 34k
5
votes
Getting integer based on string value in another field using QGIS
Here is another IMHO a bit sophisticated approach:
if("CORINE" IS NULL,
0,
map_get(
map('AG',1,'BG',2,'LW',3,'NW',4,'MW',5,'WW',6,'WA',7,'DK',8,'LN',9,'NV',11,'SU',12,'SV',13,'TM',14), …
- 34k
5
votes
Accepted
Retrieving attribute field from polygon feature containing point feature in QGIS
So, you can try either this:
aggregate(
layer:='polygon layer's name',
aggregate:='max',
expression:="polygon layer's field name",
filter:=contains($geometry, geometry(@parent))
) … or this:
aggregate(
layer:='polygon layer's name',
aggregate:='max',
expression:="polygon layer's field name",
filter:=within(geometry(@parent), $geometry)
)
Alternatively you can …
- 34k
8
votes
Accepted
Counting touching and near points for every polygon in QGIS
In QGIS there is a possibility using a "Virtual Layer" through Layer > Add Layer > Add/Edit Virtual Layer....
Let's assume there are three features in 'buildings' and 12 in 'point_layer' accordingly, …
- 34k