loess.normalize {affy} | R Documentation

## Normalize arrays

### Description

This function treats PM and MM as the raw data on each chip. It fits loess curves to MVA plots and tries to normalize the chips with respect to each other by forcing log ratios to be scattered around the same constant.

### Usage

    loess.normalize(mat, subset = sample(1:(dim(mat)[2]), 5000), epsilon
                     = 10^-2, maxit = 1, log.it = TRUE, verbose = TRUE,
                     span = 2/3, family.loess = "symmetric")

### Arguments

`mat` | a matrix with columns containing the values of the chips to normalize.
`subset` | a subset of the data to fit a loess to.
`epsilon` | small value used for the stopping criterion.
`maxit` | maximum number of iterations.
`log.it` | logical. If `TRUE` it takes the log2 of `mat`
`verbose` | logical. If `TRUE` displays current pair of chip being worked on.
`span` | span to be used by loess
`family.loess` | `"gaussian"` or `"symmetric"` as in `loess`

### Details

Experience shows that you only need 1-2 iterations to obtain useful results. This function is not written in an efficient way. In order to make it faster, loess is fit to a sample of the data which we then use to predict the curve for all the data. By setting `family.loess="gaussian"` the function is faster, but you risk losing information on differentially expressed genes. The function `normalize.quantiles` is faster.

### Value

A matrix with normalized values for chips in columns.

### Author(s)

Rafael A. Irizarry

### See Also

`normalize.quantiles`, `maffy.normalize`, `maffy.subset`

[Package affy version 1.18.2 Index]