Mega Code Archive
Generates n logarithmically-spaced points between d1 and d2 using the provided base
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import java.util.Arrays;
/**
* <p>Static methods for doing useful math</p><hr>
*
* @author : $Author: brian $
* @version : $Revision: 1.1 $
*
* <hr><p><font size="-1" color="#336699"><a href="http://www.mbari.org">
* The Monterey Bay Aquarium Research Institute (MBARI)</a> provides this
* documentation and code "as is", with no warranty, express or
* implied, of its quality or consistency. It is provided without support and
* without obligation on the part of MBARI to assist in its use, correction,
* modification, or enhancement. This information should not be published or
* distributed to third parties without specific written permission from
* MBARI.</font></p><br>
*
* <font size="-1" color="#336699">Copyright 2002 MBARI.<br>
* MBARI Proprietary Information. All rights reserved.</font><br><hr><br>
*
*/
public class Util{
/**
* generates n logarithmically-spaced points between d1 and d2 using the
* provided base.
*
* @param d1 The min value
* @param d2 The max value
* @param n The number of points to generated
* @param base the logarithmic base to use
* @return an array of lineraly space points.
*/
public static strictfp double[] logspace(double d1, double d2, int n, double base) {
double[] y = new double[n];
double[] p = linspace(d1, d2, n);
for(int i = 0; i < y.length - 1; i++) {
y[i] = Math.pow(base, p[i]);
}
y[y.length - 1] = Math.pow(base, d2);
return y;
}
/**
* generates n linearly-spaced points between d1 and d2.
* @param d1 The min value
* @param d2 The max value
* @param n The number of points to generated
* @return an array of lineraly space points.
*/
public static strictfp double[] linspace(double d1, double d2, int n) {
double[] y = new double[n];
double dy = (d2 - d1) / (n - 1);
for(int i = 0; i < n; i++) {
y[i] = d1 + (dy * i);
}
return y;
}
public static double median(double[] values) {
double[] v = new double[values.length];
double median = Double.NaN;
if (v == null || v.length == 0) {
throw new IllegalArgumentException("The data array either is null or does not contain any data.");
}
else if (v.length == 1) {
median = v[0];
}
else {
System.arraycopy(values, 0, v, 0, values.length);
Arrays.sort(v);
if (isEven(v.length)) {
int i = (int) Math.ceil(v.length / 2D);
double n1 = v[i];
double n0 = v[i - 1];
median = (n0 + n1) / 2;
}
else {
median = v[v.length / 2];
}
}
return median;
}
public static final int find(double[] array, double valueToFind) {
return Arrays.binarySearch(array, valueToFind);
}
public static double mod(double x, double y) {
double m = x;
if (y != 0) {
m = x - y * Math.floor(x / y);
}
return m;
}
public static double rem(double x, double y) {
double m = x;
if (y != 0) {
m = x - y * fix(x / y);
}
return m;
}
public static double fix(double x) {
int sign = sign(x);
double y = 0;
if (sign == -1) {
y = Math.ceil(x);
}
else if (sign == 1) {
y = Math.floor(x);
}
return y;
}
public static int sign(double x) {
int s = 0;
if (x > 0) {
s = 1;
}
else if (x < 0) {
s = -1;
}
return s;
}
/**
* Cumulatively sum a vector
* Example: cumSum([1 1 1 1 2]) = [1 2 3 4 6]
*/
public static double[] cumSum(double[] n) {
double[] buf = new double[n.length];
for (int i = 0; i < n.length; i++) {
if (i == 0) {
buf[i] = n[0];
}
else {
buf[i] = buf[i - 1] + n[i];
}
}
return buf;
}
public static boolean isEven(double x) {
double i = rem(x, 2.0);
boolean even = true;
if (i != 0.0) {
even = false;
}
return even;
}
}
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