[Boost-commit] svn:boost r38841 - sandbox/math_toolkit/libs/math/example

From: pbristow_at_[hidden]
Date: 2007-08-22 09:19:27

Author: pbristow
Date: 2007-08-22 09:19:26 EDT (Wed, 22 Aug 2007)
New Revision: 38841
URL: http://svn.boost.org/trac/boost/changeset/38841

Log:
added to examples
Text files modified: 
   sandbox/math_toolkit/libs/math/example/binomial_coinflip_example.cpp |    26 ++++++++++++++------------              
   1 files changed, 14 insertions(+), 12 deletions(-)

Modified: sandbox/math_toolkit/libs/math/example/binomial_coinflip_example.cpp
==============================================================================
--- sandbox/math_toolkit/libs/math/example/binomial_coinflip_example.cpp	(original)
+++ sandbox/math_toolkit/libs/math/example/binomial_coinflip_example.cpp	2007-08-22 09:19:26 EDT (Wed, 22 Aug 2007)
@@ -40,30 +40,29 @@
 say 0.6 for one with chewing gum on the tail,
 so it is more likely to fall tails down and heads up).
 
-First we need to some includes and using statements to be able to use the binomial distribution, and get started:
+First we need to some includes and using statements to be able to use the binomial distribution, some std input and output, and get started:
 */
 
 #include <boost/math/distributions/binomial.hpp>
   using boost::math::binomial;
 
 #include <iostream>
-  using std::cout;
-  using std::endl;
-  using std::left;
+  using std::cout;  using std::endl;  using std::left;
 #include <iomanip>
-    using std::setw;
+  using std::setw;
 
 int main()
 {
   cout << "Using Binomial distribution to predict how many heads and tails." << endl;
   try
-  { // (See note with the catch block about why try'n'catch is a good idea).
+  { // (See note with the catch block about why a try'n'catch is a good idea).
 /*`
 First, construct a binomial distribution with parameters success_fraction 1/2, and how many flips.
 */
     const double success_fraction = 0.5; // = 50% = 1/2 for a 'fair' coin.
     int flips = 10; 
     binomial flip(flips, success_fraction);
+
     cout.precision(4); // Might be able to calculate an appropriate precision from how many flips?
 /*`
  Then some examples of using Binomial moments (and echoing the parameters).
@@ -88,7 +87,7 @@
     cout << "Probability of getting no heads is " << pdf(flip, 0) << endl;
     cout << "Probability of getting at least one head is " << 1. - pdf(flip, 0) << endl;
 /*`
-But this may be inaccurate, so better to use either of
+But this last complement may be inaccurate, so better to use either of
 */
     cout << "Probability of getting 0 or 1 heads is "
       << pdf(flip, 0) + pdf(flip, 1) << endl; // sum of exactly == probabilities
@@ -100,7 +99,7 @@
 /*`
 Note that using
 */
-    cout << "Probability of getting 9 or 10 heads is " << 1 - cdf(flip, 8) << endl;
+    cout << "Probability of getting 9 or 10 heads is " << 1. - cdf(flip, 8) << endl;
 /*`
 is less accurate than using the complement
 */
@@ -124,8 +123,9 @@
       // P(X <= 7) - P(X <= 2) == P(X < 3)
       << cdf(flip, 7) - cdf(flip, 2) << endl;
     cout << endl;
+
 /*`
-Finally print two tables of probability for the exactly and at least a number of heads.
+Finally, print two tables of probability for the /exactly/ and /at least/ a number of heads.
 */
     // Print a table of probability for the exactly a number of heads.
     cout << "Probability of getting exactly (==) heads" << endl;
@@ -138,13 +138,15 @@
     } // for i
     cout << endl;
 
-    // Tabulate the probability of getting between zero and 0 to 10 heads.
+    // Tabulate the probability of getting between zero heads and 0 upto 10 heads.
     cout << "Probability of getting upto (<=) heads" << endl;
     for (int successes = 0; successes <= flips; successes++) 
-    { // Say success means getting a head (or equally success means getting a tail).
+    { // Say success means getting a head
+      // (equally success could mean getting a tail).
       double probability = cdf(flip, successes); // P(X <= heads)
       cout << setw(2) << successes << "        " << setw(10) << left
-        << probability << " or 1 in " << 1. / probability << ", or " << probability * 100. << "%"<< endl;
+        << probability << " or 1 in " << 1. / probability << ", or "
+        << probability * 100. << "%"<< endl;
     } // for i
 /*`
 The last (0 to 10 heads) must, of course, be 100% probability.