Returns a double representation of the (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient
import java.io.File;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*
*
*/
public class Main {
/**
* Returns a <code>double</code> representation of the <a
* href="http://mathworld.wolfram.com/BinomialCoefficient.html"> Binomial
* Coefficient</a>, "<code>n choose k</code>", the number of
* <code>k</code>-element subsets that can be selected from an
* <code>n</code>-element set.
* <p>
* <Strong>Preconditions</strong>:
* <ul>
* <li> <code>0 <= k <= n </code> (otherwise
* <code>IllegalArgumentException</code> is thrown)</li>
* <li> The result is small enough to fit into a <code>double</code>. The
* largest value of <code>n</code> for which all coefficients are <
* Double.MAX_VALUE is 1029. If the computed value exceeds Double.MAX_VALUE,
* Double.POSITIVE_INFINITY is returned</li>
* </ul></p>
*
* @param n the size of the set
* @param k the size of the subsets to be counted
* @return <code>n choose k</code>
* @throws IllegalArgumentException if preconditions are not met.
*/
public static double binomialCoefficientDouble(final int n, final int k) {
return Math.floor(Math.exp(binomialCoefficientLog(n, k)) + 0.5);
}
/**
* Returns the natural <code>log</code> of the <a
* href="http://mathworld.wolfram.com/BinomialCoefficient.html"> Binomial
* Coefficient</a>, "<code>n choose k</code>", the number of
* <code>k</code>-element subsets that can be selected from an
* <code>n</code>-element set.
* <p>
* <Strong>Preconditions</strong>:
* <ul>
* <li> <code>0 <= k <= n </code> (otherwise
* <code>IllegalArgumentException</code> is thrown)</li>
* </ul></p>
*
* @param n the size of the set
* @param k the size of the subsets to be counted
* @return <code>n choose k</code>
* @throws IllegalArgumentException if preconditions are not met.
*/
public static double binomialCoefficientLog(final int n, final int k) {
if (n < k) {
throw new IllegalArgumentException(
"must have n >= k for binomial coefficient (n,k)");
}
if (n < 0) {
throw new IllegalArgumentException(
"must have n >= 0 for binomial coefficient (n,k)");
}
if ((n == k) || (k == 0)) {
return 0;
}
if ((k == 1) || (k == n - 1)) {
return Math.log((double)n);
}
double logSum = 0;
// n!/k!
for (int i = k + 1; i <= n; i++) {
logSum += Math.log((double)i);
}
// divide by (n-k)!
for (int i = 2; i <= n - k; i++) {
logSum -= Math.log((double)i);
}
return logSum;
}
}
Related examples in the same category
1. | Absolute value | | |
2. | Find absolute value of float, int, double and long using Math.abs | | |
3. | Find ceiling value of a number using Math.ceil | | |
4. | Find exponential value of a number using Math.exp | | |
5. | Find floor value of a number using Math.floor | | |
6. | Find minimum of two numbers using Math.min | | |
7. | Find power using Math.pow | | |
8. | Find square root of a number using Math.sqrt | | |
9. | Find natural logarithm value of a number using Math.log | | |
10. | Find maximum of two numbers using Math.max | | |
11. | Get the power value | | |
12. | Using the Math Trig Methods | | |
13. | Using BigDecimal for Precision | | |
14. | Demonstrate our own version round() | | |
15. | Demonstrate a few of the Math functions for Trigonometry | | |
16. | Exponential Demo | | |
17. | Min Demo | | |
18. | Basic Math Demo | | |
19. | Using strict math in applications | | |
20. | Conversion between polar and rectangular coordinates | | |
21. | Using the pow() function | | |
22. | Using strict math at the method level | | |
23. | Calculating hyperbolic functions | | |
24. | Calculating trigonometric functions | | |
25. | Weighted floating-point comparisons | | |
26. | Solving right triangles | | |
27. | Applying the quadratic formula | | |
28. | Calculate the floor of the log, base 2 | | |
29. | Greatest Common Divisor (GCD) of positive integer numbers | | |
30. | Least Common Multiple (LCM) of two strictly positive integer numbers | | |
31. | Moving Average | | |
32. | Make Exponention | | |
33. | Caclulate the factorial of N | | |
34. | Trigonometric Demo | | |
35. | Complex Number Demo | | |
36. | sqrt(a^2 + b^2) without under/overflow | | |
37. | Returns an integer hash code representing the given double array value. | | |
38. | Returns an integer hash code representing the given double value. | | |
39. | Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n as a double. | | |
40. | Returns n!. Shorthand for n Factorial, the product of the numbers 1,...,n. | | |
41. | Returns the hyperbolic sine of x. | | |
42. | Contains static definition for matrix math methods. | | |
43. | For a double precision value x, this method returns +1.0 if x >= 0 and -1.0 if x < 0. Returns NaN if x is NaN. | | |
44. | For a float value x, this method returns +1.0F if x >= 0 and -1.0F if x < 0. Returns NaN if x is NaN. | | |
45. | Normalize an angle in a 2&pi wide interval around a center value. | | |
46. | Normalizes an angle to a relative angle. | | |
47. | Normalizes an angle to an absolute angle | | |
48. | Normalizes an angle to be near an absolute angle | | |
49. | Returns the natural logarithm of n!. | | |
50. | Returns the least common multiple between two integer values. | | |
51. | Gets the greatest common divisor of the absolute value of two numbers | | |
52. | Matrix manipulation | | |
53. | Returns exact (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient | | |
54. | Returns the natural log of the (http://mathworld.wolfram.com/BinomialCoefficient.html) Binomial Coefficient | | |
55. | Returns the hyperbolic cosine of x. | | |
56. | Math Utils | | |
57. | Implements the methods which are in the standard J2SE's Math class, but are not in in J2ME's. | | |
58. | Utility methods for mathematical problems. | | |
59. | A math utility class with static methods. | | |
60. | Computes the binomial coefficient "n over k" | | |
61. | Log Gamma | | |
62. | Log Beta | | |
63. | Beta | | |
64. | Gamma | | |
65. | Factorial | | |
66. | Computes p(x;n,p) where x~B(n,p) | | |
67. | Returns the sum of two doubles expressed in log space | | |
68. | sigmod | | |
69. | sigmod rev | | |
70. | Numbers that are closer than this are considered equal | | |
71. | Returns the KL divergence, K(p1 || p2). | | |
72. | Returns the sum of two doubles expressed in log space | | |
73. | Returns the difference of two doubles expressed in log space | | |
74. | Is Prime | | |
75. | Statistical functions on arrays of numbers, namely, the mean, variance, standard deviation, covariance, min and max | | |
76. | This class calculates the Factorial of a numbers passed into the program through command line arguments. | | |
77. | Calculates the Greatest Common Divisor of two numbers passed into the program through command line arguments. | | |
78. | Variance: the square of the standard deviation. | | |
79. | Population Standard Deviation | | |
80. | Returns from a static prime table the least prime that is greater than or equal to a specified value. | | |