mirror of
https://github.com/ncruces/go-sqlite3.git
synced 2026-01-12 14:09:13 +00:00
105 lines
2.6 KiB
Go
105 lines
2.6 KiB
Go
// Package stats provides aggregate functions for statistics.
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//
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// Functions:
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// - stddev_pop: population standard deviation
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// - stddev_samp: sample standard deviation
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// - var_pop: population variance
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// - var_samp: sample variance
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// - covar_pop: population covariance
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// - covar_samp: sample covariance
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//
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// See: [ANSI SQL Aggregate Functions]
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//
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// [ANSI SQL Aggregate Functions]: https://www.oreilly.com/library/view/sql-in-a/9780596155322/ch04s02.html
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package stats
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import "github.com/ncruces/go-sqlite3"
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// Register registers statistics functions.
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func Register(db *sqlite3.Conn) {
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flags := sqlite3.DETERMINISTIC | sqlite3.INNOCUOUS
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db.CreateWindowFunction("var_pop", 1, flags, newVariance(var_pop))
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db.CreateWindowFunction("var_samp", 1, flags, newVariance(var_samp))
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db.CreateWindowFunction("stddev_pop", 1, flags, newVariance(stddev_pop))
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db.CreateWindowFunction("stddev_samp", 1, flags, newVariance(stddev_samp))
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db.CreateWindowFunction("covar_pop", 2, flags, newCovariance(var_pop))
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db.CreateWindowFunction("covar_samp", 2, flags, newCovariance(var_samp))
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}
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const (
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var_pop = iota
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var_samp
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stddev_pop
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stddev_samp
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)
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func newVariance(kind int) func() sqlite3.AggregateFunction {
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return func() sqlite3.AggregateFunction { return &variance{kind: kind} }
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}
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type variance struct {
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kind int
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welford
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}
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func (fn *variance) Value(ctx sqlite3.Context) {
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var r float64
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switch fn.kind {
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case var_pop:
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r = fn.var_pop()
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case var_samp:
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r = fn.var_samp()
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case stddev_pop:
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r = fn.stddev_pop()
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case stddev_samp:
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r = fn.stddev_samp()
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}
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ctx.ResultFloat(r)
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}
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func (fn *variance) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
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if a := arg[0]; a.Type() != sqlite3.NULL {
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fn.enqueue(a.Float())
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}
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}
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func (fn *variance) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
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if a := arg[0]; a.Type() != sqlite3.NULL {
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fn.dequeue(a.Float())
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}
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}
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func newCovariance(kind int) func() sqlite3.AggregateFunction {
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return func() sqlite3.AggregateFunction { return &covariance{kind: kind} }
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}
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type covariance struct {
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kind int
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welford2
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}
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func (fn *covariance) Value(ctx sqlite3.Context) {
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var r float64
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switch fn.kind {
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case var_pop:
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r = fn.covar_pop()
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case var_samp:
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r = fn.covar_samp()
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}
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ctx.ResultFloat(r)
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}
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func (fn *covariance) Step(ctx sqlite3.Context, arg ...sqlite3.Value) {
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a, b := arg[0], arg[1]
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if a.Type() != sqlite3.NULL && b.Type() != sqlite3.NULL {
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fn.enqueue(a.Float(), b.Float())
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}
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}
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func (fn *covariance) Inverse(ctx sqlite3.Context, arg ...sqlite3.Value) {
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a, b := arg[0], arg[1]
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if a.Type() != sqlite3.NULL && b.Type() != sqlite3.NULL {
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fn.dequeue(a.Float(), b.Float())
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}
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}
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