Put the real ID of the chained line
Opened this issue · 3 comments
Hi, I found very interesting your plugin.
I have a question: what is referring to the "fid" field? I'm asking because seems there is no connection with the chained layers. It would be wonderful to have the possibility to choose a custom field in order to have the relationship to the chained node.
Regards
Roberto
Hi @ilsuocero the fid field is linked to the object id (OBJECTID)
If only one object than the fid is usualy 0.
You can show the Object ID in attribute table with $id (add a virtual field with the field calculator)
But the possibility to choose a custom field in oder to have the relationship is a good idea.
Thanks for the reply. The reason why I do not use the default id is that sometimes is null. This happens when you edit the layer in more than one step. So I created a virtual field with $id in the formula which is always updated. I named it IDF.
But IDF is not shown in the chain result so I modified in a horrible way (I'm not a python programmer) the chainagetool.py program.
This is the code, just for your knowledge:
-- coding: utf-8 --
""""
***************************************************************************
init.py - A Chainage Tool for QGIS
---------------------
begin : 2012-10-06
copyright : (C) 2012 by Werner Macho
email : werner.macho at gmail dot com
***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************
"""
from future import print_function
"""
Main Chainage definitions"""
from qgis.PyQt.QtCore import (
QVariant,
QCoreApplication
)
from qgis.core import (
QgsVectorLayer,
QgsMarkerSymbol,
QgsGeometry,
QgsProject,
QgsField,
QgsFields,
QgsFeature,
QgsMessageLog,
QgsPoint,
Qgis,
QgsSingleSymbolRenderer,
QgsVectorFileWriter,
QgsUnitTypes
)
def create_points_at(startpoint,
endpoint,
distance,
geom,
fid,
IDF,
force,
fo_fila,
divide):
"""Creating Points at coordinates along the line
"""
# don't allow distance to be zero and loop endlessly
if fo_fila:
distance = 0
if distance <= 0:
distance = geom.length()
length = geom.length()
if length < endpoint:
endpoint = length
if divide > 0:
length2 = length
if startpoint > 0:
length2 = length - startpoint
if endpoint > 0:
length2 = endpoint
if startpoint > 0 and endpoint > 0:
length2 = endpoint - startpoint
distance = length2 / divide
current_distance = distance
else:
current_distance = distance
feats = []
if endpoint > 0:
length = endpoint
# set the first point at startpoint
point = geom.interpolate(startpoint)
# convert 3D geometry to 2D geometry as OGR seems to have problems with this
point = QgsGeometry.fromPointXY(point.asPoint())
field_ID = QgsField(name="ID", type=QVariant.Int)
field_id = QgsField(name="id", type=QVariant.Int)
field = QgsField(name="dist", type=QVariant.Double)
fields = QgsFields()
fields.append(field_id)
fields.append(field)
fields.append(field_ID)
feature = QgsFeature(fields)
feature['dist'] = startpoint
feature['id'] = fid
feature['ID'] = IDF
feature.setGeometry(point)
feats.append(feature)
while startpoint + current_distance <= length:
# Get a point along the line at the current distance
point = geom.interpolate(startpoint + current_distance)
# Create a new QgsFeature and assign it the new geometry
feature = QgsFeature(fields)
feature['dist'] = (startpoint + current_distance)
feature['id'] = fid
feature['ID'] = IDF
feature.setGeometry(point)
feats.append(feature)
# Increase the distance
current_distance = current_distance + distance
# set the last point at endpoint if wanted
if force is True:
end = geom.length()
point = geom.interpolate(end)
feature = QgsFeature(fields)
feature['dist'] = end
feature['id'] = fid
feature['ID'] = IDF
feature.setGeometry(point)
feats.append(feature)
return feats
def points_along_line(layerout,
startpoint,
endpoint,
distance,
label,
layer,
selected_only=True,
force=False,
fo_fila=False,
divide=0,
decimal=2):
"""Adding Points along the line
"""
crs = layer.crs().authid()
# TODO check for virtual or shapelayer and set virt_layer according to it
shape = False
if shape:
# define fields for feature attributes. A list of QgsField objects is needed
fields = [QgsField("first", QVariant.Int),
QgsField("second", QVariant.String)]
# create an instance of vector file writer, which will create the vector file.
# Arguments:
# 1. path to new file (will fail if exists already)
# 2. encoding of the attributes
# 3. field map
# 4. geometry type - from WKBTYPE enum
# 5. layer's spatial reference (instance of
# QgsCoordinateReferenceSystem) - optional
# 6. driver name for the output file
writer = QgsVectorFileWriter("my_shapes.shp",
"CP1250",
fields,
Qgis.WKBPoint,
crs,
"ESRI Shapefile")
if writer.hasError() != QgsVectorFileWriter.NoError:
# fix_print_with_import
print("Error when creating shapefile: ", writer.hasError())
# add a feature
fet = QgsFeature()
fet.setGeometry(QgsGeometry.fromPoint(QgsPoint(10, 10)))
fet.setAttributes([1, "text"])
writer.addFeature(fet)
# delete the writer to flush features to disk (optional)
del writer
layer_type = "Shapefile" # TODO Add Shapefile functionality here
else:
layer_type = "memory"
virt_layer = QgsVectorLayer("Point?crs=%s" % crs,
layerout,
layer_type)
provider = virt_layer.dataProvider()
virt_layer.startEditing() # actually writes attributes
units = layer.crs().mapUnits()
unitname = QgsUnitTypes.toString(units)
provider.addAttributes([QgsField("fid", QVariant.Int),
QgsField("cng"+unitname, QVariant.Double),
QgsField("IDF", QVariant.Int)])
def get_features():
"""Getting the features
"""
if selected_only:
return layer.selectedFeatures()
else:
return layer.getFeatures()
# Loop through all (selected) features
for feature in get_features():
geom = feature.geometry()
#ilsuocero add custom field
attrs = feature.attributes()
IDF = attrs[6]
# Add feature ID of selected feature
fid = feature.id()
if not geom:
QgsMessageLog.logMessage("No geometry", "QChainage")
continue
features = create_points_at(startpoint,
endpoint,
distance,
geom,
fid,
IDF,
force,
fo_fila,
divide)
provider.addFeatures(features)
virt_layer.updateExtents()
proj = QgsProject.instance()
proj.addMapLayers([virt_layer])
virt_layer.commitChanges()
virt_layer.reload()
# generic labeling properties
if label:
virt_layer.setCustomProperty("labeling", "pal")
virt_layer.setCustomProperty("labeling/enabled", "true")
virt_layer.setCustomProperty("labeling/fieldName", "cng")
virt_layer.setCustomProperty("labeling/fontSize", "10")
virt_layer.setCustomProperty("labeling/multiLineLabels", "true")
virt_layer.setCustomProperty("labeling/formatNumbers", "true")
virt_layer.setCustomProperty("labeling/decimals", decimal)
virt_layer.setCustomProperty("labeling/Size", "5")
# symbol = QgsMarkerSymbol.createSimple({"name": "capital"})
# virt_layer.setRenderer(QgsSingleSymbolRenderer(symbol))
virt_layer.triggerRepaint()
return
Hi and thank you for this excellent invaluable plugin. I would like to be able to parse some of the fields to the nodes, in my case, just my calculated $length field of the line but I am sure others have fields like "name" they might prefer.
My first thought was to allow the user to pick from a dropdown/field list, which field(s) they would like to add to each chainage node, however I found this and adding a field called parent_fid that allowed for the oddity where the parent has been edited and not saved.