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/** \ingroup core
* \class QgsDateTimeStatisticalSummary
* \brief Calculator for summary statistics and aggregates for a list of datetimes.
*
* Statistics are calculated by calling @link calculate @endlink and passing a list of datetimes. The
* individual statistics can then be retrieved using the associated methods. Note that not all statistics
* are calculated by default. Statistics which require slower computations are only calculated by
* specifying the statistic in the constructor or via @link setStatistics @endlink.
*
* \note Added in version 2.16
*/
class QgsDateTimeStatisticalSummary
{
%TypeHeaderCode
#include <qgsdatetimestatisticalsummary.h>
%End
public:
//! Enumeration of flags that specify statistics to be calculated
enum Statistic
{
Count, //!< Count
CountDistinct, //!< Number of distinct datetime values
CountMissing, //!< Number of missing (null) values
Min, //!< Minimum (earliest) datetime value
Max, //!< Maximum (latest) datetime value
Range, //!< Interval between earliest and latest datetime value
All, //! All statistics
};
typedef QFlags<QgsDateTimeStatisticalSummary::Statistic> Statistics;
/** Constructor for QgsDateTimeStatisticalSummary
* @param stats flags for statistics to calculate
*/
QgsDateTimeStatisticalSummary( const QgsDateTimeStatisticalSummary::Statistics& stats = All );
/** Returns flags which specify which statistics will be calculated. Some statistics
* are always calculated (eg count).
* @see setStatistics
*/
Statistics statistics() const;
/** Sets flags which specify which statistics will be calculated. Some statistics
* are always calculated (eg count).
* @param stats flags for statistics to calculate
* @see statistics
*/
void setStatistics( const Statistics& stats );
/** Resets the calculated values
*/
void reset();
/** Calculates summary statistics for a list of variants. Any non-datetime variants will be
* ignored.
* @param values list of variants
* @see addValue()
*/
void calculate( const QVariantList& values );
/** Adds a single datetime to the statistics calculation. Calling this method
* allows datetimes to be added to the calculation one at a time. For large
* quantities of dates this may be more efficient then first adding all the
* variants to a list and calling calculate().
* @param value datetime to add. Any non-datetime variants will be ignored.
* @note call reset() before adding the first datetime using this method
* to clear the results from any previous calculations
* @note finalize() must be called after adding the final value and before
* retrieving calculated statistics.
* @see calculate()
* @see finalize()
*/
void addValue( const QVariant& value );
/** Must be called after adding all datetimes with addValue() and before retrieving
* any calculated datetime statistics.
* @see addValue()
*/
void finalize();
/** Returns the value of a specified statistic
* @param stat statistic to return
* @returns calculated value of statistic
*/
QVariant statistic( Statistic stat ) const;
/** Returns the calculated count of values.
*/
int count() const;
/** Returns the number of distinct datetime values.
*/
int countDistinct() const;
/** Returns the set of distinct datetime values.
*/
QSet< QDateTime > distinctValues() const;
/** Returns the number of missing (null) datetime values.
*/
int countMissing() const;
/** Returns the minimum (earliest) non-null datetime value.
*/
QDateTime min() const;
/** Returns the maximum (latest) non-null datetime value.
*/
QDateTime max() const;
/** Returns the range (interval between earliest and latest non-null datetime values).
*/
QgsInterval range() const;
/** Returns the friendly display name for a statistic
* @param statistic statistic to return name for
*/
static QString displayName( Statistic statistic );
};
QFlags<QgsDateTimeStatisticalSummary::Statistic> operator|(QgsDateTimeStatisticalSummary::Statistic f1, QFlags<QgsDateTimeStatisticalSummary::Statistic> f2);
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