data.DoubleFunctions Maven / Gradle / Ivy
/*
* Copyright (c) 2016 Jacob Rachiele
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software
* and associated documentation files (the "Software"), to deal in the Software without restriction
* including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense
* and/or sell copies of the Software, and to permit persons to whom the Software is furnished to
* do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or
* substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
* PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
* USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* Contributors:
*
* Jacob Rachiele
*/
package data;
import stats.Statistics;
import java.util.List;
/**
* Static methods for creating, manipulating, and operating on arrays of primitive doubles.
*
* @author Jacob Rachiele
*/
public final class DoubleFunctions {
private static final double EPSILON = Math.ulp(1.0);
private DoubleFunctions() {
}
/**
* Create and return a new array from the given data.
*
* @param data the data to create a new array from.
* @return a new array from the given data.
*/
public static double[] newArray(double... data) {
return data.clone();
}
/**
* Create a new array by combining the elements of the input arrays in the order given.
*
* @param arrays the arrays to combine.
* @return a new array formed by combining the elements of the input arrays.
*/
public static double[] combine(double[]... arrays) {
int newArrayLength = 0;
for (double[] array : arrays) {
newArrayLength += array.length;
}
double[] newArray = new double[newArrayLength];
newArrayLength = 0;
for (double[] array : arrays) {
System.arraycopy(array, 0, newArray, newArrayLength, array.length);
newArrayLength += array.length;
}
return newArray;
}
/**
* Append the given value to the end of the original array, and return the result in a new array.
*
* @param original the array to be appended.
* @param value the value to append to the end of the array.
* @return a new array consisting of the original array with the given value appended to the end.
*/
public static double[] append(double[] original, double value) {
double[] newArray = new double[original.length + 1];
System.arraycopy(original, 0, newArray, 0, original.length);
newArray[original.length] = value;
return newArray;
}
/**
* Create a new primitive double array from the given list of data.
*
* @param data the data to use in the new array.
* @return a new array from the given list of data.
*/
public static double[] newArray(List data) {
final int size = data.size();
final double[] doubles = new double[size];
for (int i = 0; i < size; i++) {
doubles[i] = data.get(i);
}
return doubles;
}
/**
* Create a new primitive double array from the given boxed Double array.
*
* @param data the data to use in the new array.
* @return a new array from the given boxed Double array.
*/
public static double[] newArray(Double[] data) {
final int size = data.length;
final double[] doubles = new double[size];
for (int i = 0; i < size; i++) {
doubles[i] = data[i];
}
return doubles;
}
/**
* Create and return a new array of the given size with every value set to the given value.
*
* @param size the number of elements of the new array.
* @param value the value to fill every element of the array with.
* @return a new array of the given size with every value set to the given value.
*/
public static double[] fill(final int size, final double value) {
final double[] filled = new double[size];
for (int i = 0; i < filled.length; i++) {
filled[i] = value;
}
return filled;
}
/**
* Return a slice of the data between the given indices.
*
* @param data the data to slice.
* @param from the starting index.
* @param to the ending index. The data at this index is excluded from the result.
* @return a slice of the data between the given indices.
*/
public static double[] slice(final double[] data, final int from, final int to) {
final double[] sliced = new double[to - from];
System.arraycopy(data, from, sliced, 0, to - from);
return sliced;
}
/**
* Transform the given data using a Box-Cox transformation with the given lambda value.
*
* @param data the data to transform.
* @param lambda the Box-Cox parameter.
* @return the data transformed using a Box-Cox transformation with the given lambda value.
*/
public static double[] boxCox(final double[] data, final double lambda) {
final double[] boxCoxed = new double[data.length];
if (Math.abs(lambda) < EPSILON) {
for (int i = 0; i < boxCoxed.length; i++) {
boxCoxed[i] = Math.log(data[i]);
}
} else {
for (int i = 0; i < boxCoxed.length; i++) {
boxCoxed[i] = (Math.pow(data[i], lambda) - 1) / lambda;
}
}
return boxCoxed;
}
/**
* Invert the Box-Cox transformation, returning the original untransformed data.
*
* @param data the transformed data to invert.
* @param lambda the Box-Cox parameter used in the transformation.
* @return the original, untransformed data in a new array.
*/
public static double[] inverseBoxCox(final double[] data, final double lambda) {
final double[] invBoxCoxed = new double[data.length];
if (Math.abs(lambda) < EPSILON) {
for (int i = 0; i < invBoxCoxed.length; i++) {
invBoxCoxed[i] = Math.exp(data[i]);
}
} else {
for (int i = 0; i < invBoxCoxed.length; i++) {
invBoxCoxed[i] = Math.pow(data[i] * lambda + 1, 1 / lambda);
}
}
return invBoxCoxed;
}
/**
* Take the square root of each element of the given array and return the result in a new array.
*
* @param data the data to take the square root of.
* @return a new array containing the square root of each element.
*/
public static double[] sqrt(final double[] data) {
final double[] sqrtData = new double[data.length];
for (int i = 0; i < sqrtData.length; i++) {
sqrtData[i] = Math.sqrt(data[i]);
}
return sqrtData;
}
/**
* Remove the mean from the given data and return the result in a new array.
*
* @param data the data to remove the mean from.
* @return the data with the mean removed.
*/
static double[] demean(final double[] data) {
final double mean = Statistics.meanOf(data);
final double[] demeaned = new double[data.length];
for (int t = 0; t < data.length; t++) {
demeaned[t] = data[t] - mean;
}
return demeaned;
}
/**
* Take the additive inverse, or negative, of each element of the given array and return the result in a new array.
*
* @param data the data to take the additive inverse of.
* @return a new array containing the additive inverse, or negative, of each element.
*/
static double[] negativeOf(final double[] data) {
final double[] negative = new double[data.length];
for (int i = 0; i < negative.length; i++) {
negative[i] = -data[i];
}
return negative;
}
}
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