medpolish {stats} R Documentation

## Median Polish of a Matrix

### Description

Fits an additive model using Tukey's median polish procedure.

### Usage

```medpolish(x, eps = 0.01, maxiter = 10, trace.iter = TRUE,
na.rm = FALSE)
```

### Arguments

 `x` a numeric matrix. `eps` real number greater than 0. A tolerance for convergence: see Details. `maxiter` the maximum number of iterations `trace.iter` logical. Should progress in convergence be reported? `na.rm` logical. Should missing values be removed?

### Details

The model fitted is additive (constant + rows + columns). The algorithm works by alternately removing the row and column medians, and continues until the proportional reduction in the sum of absolute residuals is less than `eps` or until there have been `maxiter` iterations. The sum of absolute residuals is printed at each iteration of the fitting process, if `trace.iter` is `TRUE`. If `na.rm` is `FALSE` the presence of any `NA` value in `x` will cause an error, otherwise `NA` values are ignored.

`medpolish` returns an object of class `medpolish` (see below). There are printing and plotting methods for this class, which are invoked via by the generics `print` and `plot`.

### Value

An object of class `medpolish` with the following named components:

 `overall` the fitted constant term. `row` the fitted row effects. `col` the fitted column effects. `residuals` the residuals. `name` the name of the dataset.

### References

`median`; `aov` for a mean instead of median decomposition.

### Examples

```## Deaths from sport parachuting;  from ABC of EDA, p.224:
deaths <-
rbind(c(14,15,14),
c( 7, 4, 7),
c( 8, 2,10),
c(15, 9,10),
c( 0, 2, 0))
dimnames(deaths) <- list(c("1-24", "25-74", "75-199", "200++", "NA"),
paste(1973:1975))
deaths
(med.d <- medpolish(deaths))
plot(med.d)
## Check decomposition:
all(deaths == med.d\$overall + outer(med.d\$row,med.d\$col, "+") + med.d\$resid)
```

[Package stats version 2.2.1 Index]