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Nuno Cruces
2024-01-25 11:03:33 +00:00
parent 354242e528
commit 88cf845651
3 changed files with 44 additions and 2 deletions
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6
ext/stats/stats.go
View File

@@ -17,6 +17,7 @@
// - regr_count: count non-null pairs of variables
// - regr_slope: slope of the least-squares-fit linear equation
// - regr_intercept: y-intercept of the least-squares-fit linear equation
// - regr_json: all regr stats in a JSON object
//
// These join the [Built-in Aggregate Functions]:
// - count: count rows/values
@@ -52,6 +53,7 @@ func Register(db *sqlite3.Conn) {
db.CreateWindowFunction("regr_slope", 2, flags, newCovariance(regr_slope))
db.CreateWindowFunction("regr_intercept", 2, flags, newCovariance(regr_intercept))
db.CreateWindowFunction("regr_count", 2, flags, newCovariance(regr_count))
db.CreateWindowFunction("regr_json", 2, flags, newCovariance(regr_json))
}
const (
@@ -69,6 +71,7 @@ const (
regr_slope
regr_intercept
regr_count
regr_json
)
func newVariance(kind int) func() sqlite3.AggregateFunction {
@@ -144,6 +147,9 @@ func (fn *covariance) Value(ctx sqlite3.Context) {
case regr_count:
ctx.ResultInt64(fn.regr_count())
return
case regr_json:
ctx.ResultText(fn.regr_json())
return
}
ctx.ResultFloat(r)
}

8
ext/stats/stats_test.go
View File

@@ -107,7 +107,7 @@ func TestRegister_covariance(t *testing.T) {
regr_avgy(y, x), regr_avgx(y, x),
regr_syy(y, x), regr_sxx(y, x), regr_sxy(y, x),
regr_slope(y, x), regr_intercept(y, x), regr_r2(y, x),
regr_count(y, x)
regr_count(y, x), regr_json(y, x)
FROM data`)
if err != nil {
t.Fatal(err)
@@ -151,6 +151,12 @@ func TestRegister_covariance(t *testing.T) {
if got := stmt.ColumnInt(11); got != 5 {
t.Errorf("got %v, want 5", got)
}
var a map[string]float64
if err := stmt.ColumnJSON(12, &a); err != nil {
t.Error(err)
} else if got := a["count"]; got != 5 {
t.Errorf("got %v, want 5", got)
}
}
{

32
ext/stats/welford.go
View File

@@ -1,6 +1,10 @@
package stats
import "math"
import (
"math"
"strconv"
"strings"
)
// Welford's algorithm with Kahan summation:
// https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Welford's_online_algorithm
@@ -108,6 +112,32 @@ func (w welford2) regr_r2() float64 {
return w.cov.hi * w.cov.hi / (w.m2y.hi * w.m2x.hi)
}
func (w welford2) regr_json() string {
var json strings.Builder
var num [32]byte
json.Grow(128)
json.WriteString(`{"count":`)
json.Write(strconv.AppendInt(num[:0], w.regr_count(), 10))
json.WriteString(`,"avgy":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_avgy(), 'g', -1, 64))
json.WriteString(`,"avgx":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_avgx(), 'g', -1, 64))
json.WriteString(`,"syy":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_syy(), 'g', -1, 64))
json.WriteString(`,"sxx":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_sxx(), 'g', -1, 64))
json.WriteString(`,"sxy":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_sxy(), 'g', -1, 64))
json.WriteString(`,"slope":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_slope(), 'g', -1, 64))
json.WriteString(`,"intercept":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_intercept(), 'g', -1, 64))
json.WriteString(`,"r2":`)
json.Write(strconv.AppendFloat(num[:0], w.regr_r2(), 'g', -1, 64))
json.WriteByte('}')
return json.String()
}
func (w *welford2) enqueue(y, x float64) {
w.n++
d1y := y - w.m1y.hi - w.m1y.lo