# vec2TLmom: Convert a Vector of TL-moments to a TL-moment Object In lmomco: L-Moments, Censored L-Moments, Trimmed L-Moments, L-Comoments, and Many Distributions

## Description

This function converts a vector of trimmed L-moments (TL-moments) to a TL-moment object of lmomco by dispatch to `vec2lmom`. The object is an R `list`. This function is intended to facilitate the use of TL-moments that the user might have from other sources. The trimming on the left-tail is denoted by t and the trimming on the right-tail is denoted as s. The first five TL-moments are λ^{(t,s)}_1, λ^{(t,s)}_2, λ^{(t,s)}_3, λ^{(t,s)}_4, λ^{(t,s)}_5, τ^{(t,s)}, τ^{(t,s)}_3, τ^{(t,s)}_4, and τ^{(t,s)}_5. The function supports TL-moments and TL-moment ratios of arbitrary length. Because in typical practice the k ≥ 3 order L-moments are dimensionless ratios (τ^{(t,s)}_3, τ^{(t,s)}_4, and τ^{(t,s)}_5), this function computes λ^{(t,s)}_3, λ^{(t,s)}_4, λ^{(t,s)}_5 from λ^{(t,s)}_2 and the ratios. However, typical practice is not set on the use of λ^{(t,s)}_2 or τ^{(t,s)} as measure of dispersion. Therefore, this function takes an `lscale` optional logical argument—if λ^{(t,s)}_2 is provided and `lscale=TRUE`, then τ is computed by the function and if τ is provided, then λ^{(t,s)}_2 is computed by the function. The trim level of the TL-moment is required. Lastly, it might be common for t=s and hence symmetrical trimming is used.

## Usage

 `1` ```vec2TLmom(vec, ...) ```

## Arguments

 `vec` A vector of L-moment values in λ^{(t,s)}_1, λ^{(t,s)}_2 or τ^{(t,s)}, τ^{(t,s)}_3, τ^{(t,s)}_4, and τ^{(t,s)}_5 order. `...` The arguments used by `vec2lmom`.

## Value

An R `list` is returned where t represents the `trim` level.

 `lambdas` Vector of the TL-moments. First element is λ^{(t,s)}_1, second element is λ^{(t,s)}_2, and so on. `ratios` Vector of the L-moment ratios. Second element is τ^{(t,s)}, third element is τ^{(t,s)}_3 and so on. `trim` Level of symmetrical trimming, which should equal `NULL` if asymmetrical trimming is used. `leftrim` Level of trimming of the left-tail of the sample. `rightrim` Level of trimming of the right-tail of the sample. `source` An attribute identifying the computational source of the L-moments: “TLmoms”.

## Note

The motiviation for this function that arrange trivial arguments for `vec2lmom` is that it is uncertain how TL-moments will grow in the research community and there might someday be a needed for alternative support without having to touch `vec2lmom`. Plus there is nice function name parallelism in having a dedicated function for the TL-moments as there is for L-moments and probability-weighted moments.

## Author(s)

W.H. Asquith

`TLmoms`, `vec2lmom`
 `1` ```TL <- vec2TLmom(c(12,0.6,0.34,0.20,0.05),lscale=FALSE,trim=1) ```