R: Rank-transformation to normality

rntransform {GenABEL} | R Documentation

## Rank-transformation to normality

### Description

Rank-transformation to normality of a variable or residuals from GLM analysis.

### Usage

    rntransform(formula,data,family=gaussian)

### Arguments

`formula` | GLM formula for the variable to be transformed, or just the variable
`data` | data.frame or gwaa.data object containing the data
`family` | GLM family

### Details

Rank-transformation to normality generates perfectly normal distribution from ANY distribution, unless many/heavy ties are present in variable (or residuals, if formula is used).

When formula is supplied, this procedure first calls `ztransform`, and then applies rank transformation to residuals.

### Value

Vector containing transformed variable, distributed as standard normal.

### Author(s)

Yurii Aulchenko

### See Also

`ztransform`

### Examples

    	# uniformly distributed variable
    	x <- round(runif(200)*100)
    	# get 7 missing values
    	x[round(runif(7,min=1,max=100))] <- NA
    	# Z-transform
    	y0 <- ztransform(x)
    	# Rank-transform to normality
    	y1 <- rntransform(x)
    	# test normality of the original and transformed var
    	shapiro.test(x)
    	shapiro.test(y0)
    	shapiro.test(y1)
    	# plot histogram
    	par(mfcol=c(3,1))
    	hist(x)
    	hist(y0)
    	hist(y1)

[Package GenABEL version 1.8-0 Index]