/
statistics.go
55 lines (49 loc) · 1.37 KB
/
statistics.go
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// Copyright 2018 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package core
import (
"github.com/montanaflynn/stats"
)
// RollingStats provides rolling statistics with specified window size.
// There are window size records for calculating.
type RollingStats struct {
records []float64
size int
count int
}
// NewRollingStats returns a RollingStats.
func NewRollingStats(size int) *RollingStats {
return &RollingStats{
records: make([]float64, size),
size: size,
}
}
// Add adds an element.
func (r *RollingStats) Add(n float64) {
r.records[r.count%r.size] = n
r.count++
}
// Median returns the median of the records.
// it can be used to filter noise.
// References: https://en.wikipedia.org/wiki/Median_filter.
func (r *RollingStats) Median() float64 {
if r.count == 0 {
return 0
}
records := r.records
if r.count < r.size {
records = r.records[:r.count]
}
median, _ := stats.Median(records)
return median
}