Diskussion:Workshop QGIS Python GeoPython 2017 - Versionsgeschichte

Stefan: /* Usage of Expression Functions */

2018-04-19T23:10:32Z

Usage of Expression Functions

← Nächstältere Version		Version vom 19. April 2018, 23:10 Uhr
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	== Usage of Expression Functions ==		== Usage of Expression Functions ==

	~~This is a list of places~~ where Expression Functions (EFns) can be used in QGIS:		Examples where Expression Functions (EFns) can be used in QGIS are: symbology, labeling, calculating fields, defining virtual fields, selecting and filtering data, layouts, atlas serial printing and reports, map tips, custom python expressions, parameters for processing, and many more.

			This is a more systematic list:
	# "Server-side" / data-related:		# "Server-side" / data-related:
	## "Select features using an expression" based on a field(Layer property).		## "Select features using an expression" based on a field(Layer property).
Zeile 22:		Zeile 24:
	## "Rule based labeling" (drop-down menu) in Layer Properties > Labels; click on '+' button and add a EFn based filter to a field.		## "Rule based labeling" (drop-down menu) in Layer Properties > Labels; click on '+' button and add a EFn based filter to a field.
	## Part of "Geometry generator" for geometry field in "Style > Symbol Layer Type"		## Part of "Geometry generator" for geometry field in "Style > Symbol Layer Type"
	~~''(Add other places to the list above if you find more)''.~~

	== Possible examples of custom Custom Expression Functions ==		== Possible examples of custom Custom Expression Functions ==

Stefan: /* Possible examples of custom Custom Expression Functions */

2017-05-07T21:37:35Z

Possible examples of custom Custom Expression Functions

← Nächstältere Version		Version vom 7. Mai 2017, 21:37 Uhr
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	# Function for remote webservice: geocoding (reading from the internet).		# Function for remote webservice: geocoding (reading from the internet).
	# Function reading from other layers (out of scope for a workshop rather, ev. also a processing or plugin candidate).		# Function reading from other layers (out of scope for a workshop rather, ev. also a processing or plugin candidate).

	Here's a use case: A user wants to create a layer (table) which as a primary key (id) which behaves like 'autoincrement' when user edit a new feature. So user does not have to care about unique, sequential values for the PK, like autoincrement in MySQL). In QGIS 3 this is available when user chooses "UNIQUE" as constraint. In QGIS 2.18 (or before) there is a clever custom expression function needed. => Solution?

	== Notes ==		== Notes ==

Stefan: /* Possible examples of custom Custom Expression Functions */

2017-05-07T20:54:13Z

Possible examples of custom Custom Expression Functions

← Nächstältere Version		Version vom 7. Mai 2017, 20:54 Uhr
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	# Functions reading something like a "Singleton" like a system environment variable (usage "env('USERNAME')") layer properties or number sequence (spcial Plugin needed?).		# Functions reading something like a "Singleton" like a system environment variable (usage "env('USERNAME')") layer properties or number sequence (spcial Plugin needed?).
	# Function for remote webservice: geocoding (reading from the internet).		# Function for remote webservice: geocoding (reading from the internet).
	# ~~Out of scope:~~ Function reading from other layers (rather ~~candidate for~~ a plugin).		# Function reading from other layers (out of scope for a workshop rather, ev. also a processing or plugin candidate).

	~~After the GeoPython Workshop, Simran makes pull request to Expression Plus Plugin adding "env()" fn.~~		Here's a use case: A user wants to create a layer (table) which as a primary key (id) which behaves like 'autoincrement' when user edit a new feature. So user does not have to care about unique, sequential values for the PK, like autoincrement in MySQL). In QGIS 3 this is available when user chooses "UNIQUE" as constraint. In QGIS 2.18 (or before) there is a clever custom expression function needed. => Solution?

	~~Optional (but highly demanded)~~ use case: A user wants to create a layer (table) which as a primary key (id) which behaves like 'autoincrement' when user edit a new feature. So user does not have to care about unique, sequential values for the PK, like autoincrement in MySQL). In QGIS 3 this is available when user chooses "UNIQUE" as constraint. In QGIS 2.18 (or before) there is a clever custom expression function needed. => Solution?

	== Notes ==		== Notes ==

Stefan: /* Usage of Expression Functions */

2017-05-07T20:30:27Z

Usage of Expression Functions

Stefan: /* Usage of Expression Functions */

2017-05-07T20:23:03Z

Usage of Expression Functions

← Nächstältere Version		Version vom 7. Mai 2017, 20:23 Uhr
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	## "Statistical Summary" Panel (Layer property).		## "Statistical Summary" Panel (Layer property).
	## "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set CEF based values for page name, filter and output filename.		## "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set CEF based values for page name, filter and output filename.
			## Processing
	# "Client-side" / style-related:		# "Client-side" / style-related:
	## "Map Tip" tool (Layer property).		## "Map Tip" tool (Layer property).

Stefan am 7. Mai 2017 um 12:42 Uhr

2017-05-07T12:42:45Z

← Nächstältere Version		Version vom 7. Mai 2017, 12:42 Uhr
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	* https://etherpad.coredump.ch/p/Python-Workshop		* https://etherpad.coredump.ch/p/Python-Workshop

	~~User Defined or ''Custom~~ Expression Functions (~~custom~~ EFns)'' can be used in ~~...~~		== Usage of Expression Functions ==

			This is a list of places where Expression Functions (EFns) can be used in QGIS:
	# "Server-side" / data-related:		# "Server-side" / data-related:
	## "Select features using an expression" (Layer property).		## "Select features using an expression" (Layer property).
Zeile 21:		Zeile 23:
	''(Add other places to the list above if you find more)''.		''(Add other places to the list above if you find more)''.

	== Possible examples ==		== Possible examples of custom Custom Expression Functions ==
	# Function doing something "local" like from other field(s).		# Function doing something "local" like from other field(s).
	# Functions reading something like a "Singleton" like a system environment variable (usage "env('USERNAME')") layer properties or number sequence (spcial Plugin needed?).		# Functions reading something like a "Singleton" like a system environment variable (usage "env('USERNAME')") layer properties or number sequence (spcial Plugin needed?).

Stefan am 7. Mai 2017 um 12:40 Uhr

2017-05-07T12:40:42Z

← Nächstältere Version		Version vom 7. Mai 2017, 12:40 Uhr
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	## "Rule based labeling". Layer Properties > Labels > Select Rule based labeling from the drop-down menu > Click on the '+' button and add a CEF based filter (... button).		## "Rule based labeling". Layer Properties > Labels > Select Rule based labeling from the drop-down menu > Click on the '+' button and add a CEF based filter (... button).
	## Part of "Geometry generator" in "Style > Symbol Layer Type"		## Part of "Geometry generator" in "Style > Symbol Layer Type"


	''(Add other places to the list above if you find more)''.		''(Add other places to the list above if you find more)''.


	== Possible examples ==		== Possible examples ==

Stefan am 7. Mai 2017 um 12:40 Uhr

2017-05-07T12:40:11Z

← Nächstältere Version		Version vom 7. Mai 2017, 12:40 Uhr
Zeile 4:		Zeile 4:
	* https://etherpad.coredump.ch/p/Python-Workshop		* https://etherpad.coredump.ch/p/Python-Workshop

	User Defined or ''Custom Expression Functions (custom ~~EFs~~)'' can be used in ...		User Defined or ''Custom Expression Functions (custom EFns)'' can be used in ...
	# "Layer > Properties > Tab Fields" in Button "Text Edit" in Default- and in Constraints-Field.		# "Server-side" / data-related:
	# "Layer > Properties > Tab Style" in "Label with".		## "Select features using an expression" (Layer property).
	# ~~"Select features using an expression".~~		## "Filtering features" while loading from source. Switch to the form view in the attribute table (button on bottom right corner) > click on 'Show All Features' (bottom left) and select 'Advanced Filter (Expression)'.
	# "Field Calculator".		## "Layer > Properties > Tab Fields" in Button "Text Edit" in Default- and in Constraints-Field.
	# ~~"Statistical Summary" Panel.~~		## "Layer > Properties > Tab Style" in "Label with".
	~~# "Map Tip" tool.~~		## "Field Calculator" to defining new or virtual fields (Layer property).
	# "Conditional formatting" in the attribute table (Create a new rule and set the condition to the output of a custom EF).		## "Conditional formatting" in the attribute table (Create a new rule and set the condition to the output of a custom EFn).
	# "~~Filtering features~~"~~. Switch to the form view in the attribute table~~ (~~button on bottom right corner) > click on 'Show All Features' (bottom left) and select 'Advanced Filter (Expression~~)'.		# Analysis-related:
	# "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set CEF based values for page name, filter and output filename.		## "Statistical Summary" Panel (Layer property).
	# "Rule based labeling". Layer Properties > Labels > Select Rule based labeling from the drop-down menu > Click on the '+' button and add a CEF based filter (... button).		## "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set CEF based values for page name, filter and output filename.
	# Part of "Geometry generator" in "Style > Symbol Layer Type"		# "Client-side" / style-related:
	# ''(~~add~~ other places ~~here~~)''		## "Map Tip" tool (Layer property).
			## "Rule based labeling". Layer Properties > Labels > Select Rule based labeling from the drop-down menu > Click on the '+' button and add a CEF based filter (... button).
			## Part of "Geometry generator" in "Style > Symbol Layer Type"


			''(Add other places to the list above if you find more)''.

Stefan am 6. Mai 2017 um 22:39 Uhr

2017-05-06T22:39:28Z

← Nächstältere Version		Version vom 6. Mai 2017, 22:39 Uhr
Zeile 4:		Zeile 4:
	* https://etherpad.coredump.ch/p/Python-Workshop		* https://etherpad.coredump.ch/p/Python-Workshop

	User Defined or ''Custom Expression Functions (~~CEFs~~)'' can be used in ...		User Defined or ''Custom Expression Functions (custom EFs)'' can be used in ...
	# "Layer > Properties > Tab Fields" in Button "Text Edit" in Default- and in Constraints-Field.		# "Layer > Properties > Tab Fields" in Button "Text Edit" in Default- and in Constraints-Field.
	# "Layer > Properties > Tab Style" in "Label with".		# "Layer > Properties > Tab Style" in "Label with".
Zeile 10:		Zeile 10:
	# "Field Calculator".		# "Field Calculator".
	# "Statistical Summary" Panel.		# "Statistical Summary" Panel.
	# "Map Tip" tool		# "Map Tip" tool.
	# "Conditional formatting" in the attribute table (Create a new rule and set the condition to the output of a ~~CEF~~).		# "Conditional formatting" in the attribute table (Create a new rule and set the condition to the output of a custom EF).
	# "Filtering features". Switch to the form view in the attribute table (button on bottom right corner) > click on 'Show All Features' (bottom left) and select 'Advanced Filter (Expression)'.		# "Filtering features". Switch to the form view in the attribute table (button on bottom right corner) > click on 'Show All Features' (bottom left) and select 'Advanced Filter (Expression)'.
	# "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set CEF based values for page name, filter and output filename.		# "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set CEF based values for page name, filter and output filename.
	# "Rule based labeling". Layer Properties > Labels > Select Rule based labeling from the drop-down menu > Click on the '+' button and add a CEF based filter (... button).		# "Rule based labeling". Layer Properties > Labels > Select Rule based labeling from the drop-down menu > Click on the '+' button and add a CEF based filter (... button).
	# (other places?)		# Part of "Geometry generator" in "Style > Symbol Layer Type"
			# ''(add other places here)''

Simran am 5. Mai 2017 um 09:59 Uhr

2017-05-05T09:59:05Z

← Nächstältere Version		Version vom 5. Mai 2017, 09:59 Uhr
Zeile 11:		Zeile 11:
	# "Statistical Summary" Panel.		# "Statistical Summary" Panel.
	# "Map Tip" tool		# "Map Tip" tool
	# Conditional formatting in attribute table		# "Conditional formatting" in the attribute table (Create a new rule and set the condition to the output of a CEF).
	# Rule based labeling		# "Filtering features". Switch to the form view in the attribute table (button on bottom right corner) > click on 'Show All Features' (bottom left) and select 'Advanced Filter (Expression)'.
			# "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set CEF based values for page name, filter and output filename.
			# "Rule based labeling". Layer Properties > Labels > Select Rule based labeling from the drop-down menu > Click on the '+' button and add a CEF based filter (... button).
	# (other places?)		# (other places?)


	== Possible examples ==		== Possible examples ==

← Nächstältere Version		Version vom 7. Mai 2017, 20:30 Uhr
Zeile 8:		Zeile 8:
	This is a list of places where Expression Functions (EFns) can be used in QGIS:		This is a list of places where Expression Functions (EFns) can be used in QGIS:
	# "Server-side" / data-related:		# "Server-side" / data-related:
	## "Select features using an expression" (Layer property).		## "Select features using an expression" based on a field(Layer property).
	## "Filtering features" while loading from source. ~~Switch to the~~ form view ~~in the attribute~~ table (button on bottom right corner) > click on 'Show All Features' (bottom left) and select 'Advanced Filter (Expression)'.		## "Filtering features" while loading from source. See form view of Attribute table (button on bottom right corner) > click on 'Show All Features' (bottom left) and select 'Advanced Filter (Expression)'.
	## "Layer > Properties > Tab Fields" in Button "Text Edit" in ~~Default~~- and in ~~Constraints-Field~~.		## "Layer > Properties > Tab Fields" in Button "Text Edit" in default- and in constraints field.
	## "Layer > Properties > Tab Style" in "Label with".		## "Layer > Properties > Tab Style" in "Label with" field.
	## "Field Calculator" to defining new or virtual fields (Layer property).		## "Field Calculator" to defining new or virtual fields (Layer property).
	## "Conditional formatting" in ~~the attribute~~ table (Create a new rule and set the condition to the output of a custom EFn).		## "Conditional formatting" of a field in Attribute table (Create a new rule and set the condition to the output of a custom EFn).
	# Analysis-related:		# Analysis-related:
	## "Statistical Summary" ~~Panel (Layer property)~~.		## "Statistics Panel" / "Statistical Summary" of a field.
	## "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set ~~CEF~~ based values for page name, filter and output filename.		## "Atlas Generation" in the Print Composer. Project > Print Composer > Check 'generate an atlas' > Set EFn based values for page name, filter and output filename.
	## Processing		## Processing
	# "Client-side" / style-related:		# "Client-side" / style-related:
	## "Map Tip" tool (Layer property).		## "Map Tip" tool (Layer property).
	## "Rule based labeling"~~. Layer Properties > Labels > Select Rule based labeling from the~~ drop-down menu > ~~Click~~ on ~~the~~ '+' button and add a ~~CEF~~ based filter ~~(... button)~~.		## "Rule based labeling" (drop-down menu) in Layer Properties > Labels; click on '+' button and add a EFn based filter to a field.
	## Part of "Geometry generator" in "Style > Symbol Layer Type"		## Part of "Geometry generator" for geometry field in "Style > Symbol Layer Type"
	''(Add other places to the list above if you find more)''.		''(Add other places to the list above if you find more)''.