9 Commits

Author	SHA1	Message	Date
Nyall Dawson	307aabd66a	[FEATURE] Aggregates for expressions ... 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	2016-05-17 10:53:25 +10:00
Nyall Dawson	1c45b940a8	Add calculation of number of null values to QgsStatisticalSummary	2016-05-17 10:53:04 +10:00
Nyall Dawson	4dea723cae	Add methods to stats calculators to accept values one at a time ... This can be more efficient for large quantities of values, since it avoids the need to create a list of all values in advance	2016-05-17 10:52:06 +10:00
Nyall Dawson	e15962eea9	[processing] Use QgsStatisticalSummary for statistic calculations ... For BasicStatisticssNumbers and StatisticsByCategories algorithms. Adds extra stats (minority, majority, 1st/3rd quartile and IQR) while avoiding custom statistics calculation code.	2015-11-16 15:04:34 +11:00
Nyall Dawson	c49b5b777f	Change a lot of arguments to const references in core/gui ... Rationale: - there was a lot of large objects passed by value, so potentially there's a speed bump from this - even for implicitly shared classes like QString/QList there's still a (small) cost for copying the objects when there's no reason to - it's the right thing to do!	2015-10-07 12:02:04 +11:00
Nyall Dawson	e7b7549c29	[FEATURE] New statistical summary dock widget ... Can display summary statistics (eg mean, standard deviation, ...) for a field or expression from a vector layer.	2015-05-23 04:35:11 +10:00
Juergen E. Fischer	edeafa95ac	indentation and minor sip updates	2015-05-03 17:10:32 +02:00
Nyall Dawson	31e8611230	Add quartiles and IQR to QgsStatisticalSummary calculations	2015-05-03 20:48:22 +10:00
Nyall Dawson	154468bd84	Add QgsStatisticalSummary class for calculating stats from a list ... of values.	2015-05-02 23:19:39 +10:00