QuantLib_GeneralStatistics man page
GeneralStatistics — Statistics tool.
Synopsis
#include <ql/math/statistics/generalstatistics.hpp>
Public Types
typedef Real value_type
Public Member Functions
Inspectors
Size samples () const
number of samples collected
const std::vector< std::pair< Real, Real > > & data () const
collected data
Real weightSum () const
sum of data weights
Real mean () const
Real variance () const
Real standardDeviation () const
Real errorEstimate () const
Real skewness () const
Real kurtosis () const
Real min () const
Real max () const
template<class Func , class Predicate > std::pair< Real, Size > expectationValue (const Func &f, const Predicate &inRange) const
Real percentile (Real y) const
Real topPercentile (Real y) const
Modifiers
void add (Real value, Real weight=1.0)
adds a datum to the set, possibly with a weight
template<class DataIterator > void addSequence (DataIterator begin, DataIterator end)
adds a sequence of data to the set, with default weight
template<class DataIterator , class WeightIterator > void addSequence (DataIterator begin, DataIterator end, WeightIterator wbegin)
adds a sequence of data to the set, each with its weight
void reset ()
resets the data to a null set
void reserve (Size n) const
informs the internal storage of a planned increase in size
void sort () const
sort the data set in increasing order
Detailed Description
Statistics tool.
This class accumulates a set of data and returns their statistics (e.g: mean, variance, skewness, kurtosis, error estimation, percentile, etc.) based on the empirical distribution (no gaussian assumption)
It doesn't suffer the numerical instability problem of IncrementalStatistics. The downside is that it stores all samples, thus increasing the memory requirements.
Member Function Documentation
Real mean () const
returns the mean, defined as [ langle x rangle = ac{sum w_i x_i}{sum w_i}. ]
Real variance () const
returns the variance, defined as [ sigma^2 = ac{N}{N-1} leftlangle left( x-langle x rangle right)^2 rightrangle. ]
Real standardDeviation () const
returns the standard deviation $ sigma $, defined as the square root of the variance.
Real errorEstimate () const
returns the error estimate on the mean value, defined as $ \psilon = sigma/sqrt{N}. $
Real skewness () const
returns the skewness, defined as [ ac{N^2}{(N-1)(N-2)} ac{leftlangle left( x-langle x rangle right)^3 rightrangle}{sigma^3}. ] The above evaluates to 0 for a Gaussian distribution.
Real kurtosis () const
returns the excess kurtosis, defined as [ ac{N^2(N+1)}{(N-1)(N-2)(N-3)} ac{leftlangle left(x-langle x rangle right)^4 rightrangle}{sigma^4} - ac{3(N-1)^2}{(N-2)(N-3)}. ] The above evaluates to 0 for a Gaussian distribution.
Real min () const
returns the minimum sample value
Real max () const
returns the maximum sample value
std::pair<Real,Size> expectationValue (const Func & f, const Predicate & inRange) const
Expectation value of a function $ f $ on a given range $ mathcal{R} $, i.e., [ mathrm{E}left[f ;|; mathcal{R}right] = ac{sum_{x_i in mathcal{R}} f(x_i) w_i}{ sum_{x_i in mathcal{R}} w_i}. ] The range is passed as a boolean function returning true
if the argument belongs to the range or false
otherwise.
The function returns a pair made of the result and the number of observations in the given range.
Real percentile (Real y) const
$ y $-th percentile, defined as the value $ bar{x} $ such that [ y = ac{sum_{x_i < bar{x}} w_i}{ sum_i w_i} ]
Precondition:
$ y $ must be in the range $ (0-1]. $
Real topPercentile (Real y) const
$ y $-th top percentile, defined as the value $ bar{x} $ such that [ y = ac{sum_{x_i > bar{x}} w_i}{ sum_i w_i} ]
Precondition:
$ y $ must be in the range $ (0-1]. $
void add (Real value, Real weight = 1.0)
adds a datum to the set, possibly with a weight
- Precondition:
weights must be positive or null
Author
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Referenced By
The man pages errorEstimate(3), expectationValue(3), kurtosis(3), max(3), mean(3), min(3), reserve(3), samples(3), skewness(3), sort(3), standardDeviation(3), topPercentile(3) and weightSum(3) are aliases of QuantLib_GeneralStatistics(3).