# impRZalr: alr EM-based imputation of rounded zeros In robCompositions: Compositional Data Analysis

 impRZalr R Documentation

## alr EM-based imputation of rounded zeros

### Description

A modified EM alr-algorithm for replacing rounded zeros in compositional data sets.

### Usage

``````impRZalr(
x,
pos = ncol(x),
dl = rep(0.05, ncol(x) - 1),
eps = 1e-04,
maxit = 50,
bruteforce = FALSE,
method = "lm",
step = FALSE,
nComp = "boot",
R = 10,
verbose = FALSE
)
``````

### Arguments

 `x` compositional data `pos` position of the rationing variable for alr transformation `dl` detection limit for each part `eps` convergence criteria `maxit` maximum number of iterations `bruteforce` if TRUE, imputations over dl are set to dl. If FALSE, truncated (Tobit) regression is applied. `method` either “lm” (default) or “MM” `step` if TRUE, a stepwise (AIC) procedure is applied when fitting models `nComp` if determined, it fixes the number of pls components. If “boot”, the number of pls components are estimated using a bootstraped cross validation approach. `R` number of bootstrap samples for the determination of pls components. Only important for method “pls”. `verbose` additional print output during calculations.

### Details

Statistical analysis of compositional data including zeros runs into problems, because log-ratios cannot be applied. Usually, rounded zeros are considerer as missing not at random missing values. The algorithm first applies an additive log-ratio transformation to the compositions. Then the rounded zeros are imputed using a modified EM algorithm.

### Value

 `xOrig ` Original data frame or matrix `xImp ` Imputed data `wind ` Index of the missing values in the data ```iter ``` Number of iterations `eps ` eps

### Author(s)

Matthias Templ and Karel Hron

### References

Palarea-Albaladejo, J., Martin-Fernandez, J.A. Gomez-Garcia, J. (2007) A parametric approach for dealing with compositional rounded zeros. Mathematical Geology, 39(7), 625-645.

`impRZilr`

### Examples

``````
data(arcticLake)
x <- arcticLake
## generate rounded zeros artificially:
x[x[,1] < 5, 1] <- 0
x[x[,2] < 47, 2] <- 0
xia <- impRZalr(x, pos=3, dl=c(5,47), eps=0.05)
xia\$xImp

``````

robCompositions documentation built on Aug. 25, 2023, 5:13 p.m.