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/*
* Copyright 2020-2021 Dynatrace LLC
*
* 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 com.dynatrace.dynahist.quantile;
import java.util.function.LongToDoubleFunction;
/** A quantile estimator. */
@FunctionalInterface
public interface QuantileEstimator {
/**
* Estimates the quantile from sorted data which can be randomly accessed through the given
* function.
*
* If numValues is equal to 0 the return value will always be {@link Double#isNaN()}.
*
*
The behavior is undefined, if the given function is not monotonic increasing.
*
* @param p specifies the quantile, must be in [0,1], e.g. 0.5 specifies the median
* @param sortedValueFunction a function that gives access the i-th largest (0-based) value if the
* argument is equal to i, the function must accept any nonnegative arguments less than
* numValues
* @param numValues the number of values
* @return the quantile estimate
*/
double estimateQuantile(
final double p, final LongToDoubleFunction sortedValueFunction, final long numValues);
/**
* Estimates the quantile from a sorted double array.
*
*
If numValues is equal to 0 the return value will always be {@link Double#isNaN()}.
*
*
The behavior is undefined, if the array is not sorted in ascending order.
*
* @param p specifies the quantile, must be in [0,1], e.g. 0.5 specifies the median
* @param sortedValues a sorted double array
* @return the quantile estimate
*/
default double estimateQuantile(final double p, double[] sortedValues) {
return estimateQuantile(p, i -> sortedValues[(int) i], sortedValues.length);
}
}