std:: lognormal_distribution
From cppreference.com
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Defined in header
<random>
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||
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template
<
class
RealType
=
double
>
class lognormal_distribution ; |
(since C++11) | |
The lognormal_distribution random number distribution produces random numbers x > 0 according to a Log-normal distribution :
-
f(x; m,s) =
exp ⎛1 sx √ 2 π
⎜
⎝ -
⎞(ln x - m) 2 2s 2
⎟
⎠
The parameters m and s are, respectively, the mean and standard deviation of the natural logarithm of x .
std::lognormal_distribution
satisfies all requirements of
RandomNumberDistribution
.
Template parameters
| RealType | - | The result type generated by the generator. The effect is undefined if this is not one of float , double , or long double . |
Member types
| Member type | Definition |
result_type
(C++11)
|
RealType |
param_type
(C++11)
|
the type of the parameter set, see RandomNumberDistribution . |
Member functions
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(C++11)
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constructs new distribution
(public member function) |
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(C++11)
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resets the internal state of the distribution
(public member function) |
Generation |
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(C++11)
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generates the next random number in the distribution
(public member function) |
Characteristics |
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|
(C++11)
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returns the distribution parameters
(public member function) |
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(C++11)
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gets or sets the distribution parameter object
(public member function) |
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(C++11)
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returns the minimum potentially generated value
(public member function) |
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(C++11)
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returns the maximum potentially generated value
(public member function) |
Non-member functions
|
(C++11)
(C++11)
(removed in C++20)
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compares two distribution objects
(function) |
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(C++11)
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performs stream input and output on pseudo-random number distribution
(function template) |
Example
Run this code
#include <cmath> #include <iomanip> #include <iostream> #include <map> #include <random> #include <string> int main() { std::random_device rd; std::mt19937 gen(rd()); std::lognormal_distribution<> d(1.6, 0.25); std::map<int, int> hist; for (int n = 0; n < 1e4; ++n) ++hist[std::round(d(gen))]; for (std::cout << std::fixed << std::setprecision(1); auto [x, y] : hist) std::cout << std::hex << x << ' ' << std::string(y / 200, '*') << '\n'; }
Possible output:
2 3 *** 4 ************* 5 *************** 6 ********* 7 **** 8 * 9 a b c
External links
| Weisstein, Eric W. "Log Normal Distribution." From MathWorld — A Wolfram Web Resource. |