io.trino.operator.aggregation.state.CovarianceState Maven / Gradle / Ivy
/*
* 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 io.trino.operator.aggregation.state;
import io.trino.spi.function.AccumulatorState;
public interface CovarianceState
extends AccumulatorState
{
long getCount();
void setCount(long value);
double getMeanX();
void setMeanX(double value);
double getMeanY();
void setMeanY(double value);
double getC2();
void setC2(double value);
default void update(double x, double y)
{
long n = getCount() + 1;
setCount(n);
double oldMeanX = getMeanX();
setMeanX(oldMeanX + (x - oldMeanX) / n);
double oldMeanY = getMeanY();
double newMeanY = oldMeanY + (y - oldMeanY) / n;
setMeanY(newMeanY);
setC2(getC2() + (x - oldMeanX) * (y - newMeanY));
}
default void merge(CovarianceState otherState)
{
if (otherState.getCount() == 0) {
return;
}
long na = getCount();
long nb = otherState.getCount();
long n = na + nb;
setCount(n);
double meanX = getMeanX();
double meanY = getMeanY();
double deltaX = otherState.getMeanX() - meanX;
double deltaY = otherState.getMeanY() - meanY;
setC2(getC2() + otherState.getC2() + deltaX * deltaY * na * nb / (double) n);
setMeanX(meanX + deltaX * nb / (double) n);
setMeanY(meanY + deltaY * nb / (double) n);
}
default double getCovarianceSample()
{
return getC2() / (getCount() - 1);
}
default double getCovariancePopulation()
{
return getC2() / getCount();
}
}