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app_stats.go
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/
app_stats.go
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// Copyright 2017 The Cockroach Authors.
//
// 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
// implied. See the License for the specific language governing
// permissions and limitations under the License.
package roachpb
// GetVariance retrieves the variance of the values.
func (l *NumericStat) GetVariance(count int64) float64 {
return l.SquaredDiffs / (float64(count) - 1)
}
// Record adjusts the derived statistics for a new value.
func (l *NumericStat) Record(count int64, val float64) {
delta := val - l.Mean
l.Mean += delta / float64(count)
l.SquaredDiffs += delta * (val - l.Mean)
}