Transformation to standard Normal

ztransform {GenABEL}R Documentation

Transformation to standard Normal

Description

Transformation of a variable or residuals from GLM analysis to standard Normal.

Usage

ztransform(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

Transformation to normality generates a variable which has mean zero and variance of one. If formula used, residuals from regression model are scaled to standard Normal.

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 1.6-7 Index]