# momentList: Class momentList In CharlotteJana/momcalc: Symbolic Moment Calculation

## Description

Create and validate objects of class `momentList`. Class `momentList` is needed as argument for function `transformMoment`. The returned value of `transformMoment` is of class `momentList`, too. The class provides a convenient structure to store moments of a multidimensional distribution.

Class `momentList` consists of four elements: Element `centralMoments` contains all known central moments of the distribution, where as `rawMoments` contains all raw moments of the distribution. Both are stored as list. The elements `centralMomentOrders` and `rawMomentOrders` contain the corresponding orders of the moments. They are stored as matrix or data.frame, each row represents one order of the moment. The number of columns of these matrices should be equal to the dimension of the distribution.

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12``` ```new_momentList(rawMomentOrders = NULL, rawMoments = list(), centralMomentOrders = NULL, centralMoments = list()) momentList(rawMomentOrders = NULL, rawMoments = list(), centralMomentOrders = NULL, centralMoments = list(), warnings = TRUE, replace = FALSE) validate_momentList(x, warnings = TRUE, replace = FALSE) extractMean(x, ...) extractCov(x) ```

## Arguments

 `rawMomentOrders` matrix or data.frame. Every row gives the order of a raw moment that is already known. `rawMoments` list. The i-th entry is the raw Moment of order `rawMomentOrders[i, ]`. `centralMomentOrders` matrix or data.frame. Every row gives the order of a central moment that is already known. `centralMoments` list. The i-th entry is the central Moment of order `centralMomentOrders[i, ]`. `warnings` bool. If FALSE, warnings about moments of order 0 and 1 will be suppressed. `replace` bool. If TRUE, inconvenient values of moments of order 0 and 1 will be replaced by convenient ones. `x` object of class `momentList` `...` additional arguments to function mean. They are currently not used.

## Details

There are five different functions available for this class:
Function `new_momentList` is a low level constructor that does not check for correct types of the arguments or if they fit together. It should be only used with care.
Function `momentList` creates an object of class `momentList` and performs various checks on the elements. Most of them are executed within function `validate_momentList`. This function particularly checks for moments of order one and zero. If they contain false values, a warning will be thrown. If moments of these orders are not contained in `momentList`, they are added automatically.
The functions `extractMean` and `extractCov` pick the means or covariances out of momentList in case they exist. Function `extracCov` may transform raw moments of order two into covariances, if the corresponding central moments are not given.

CharlotteJana/momcalc documentation built on Oct. 17, 2019, 7:21 a.m.