| ztransform {GenABEL} | R Documentation |
Transformation of a variable or residuals from GLM analysis to standard Normal.
ztransform(formula,data,family=gaussian)
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 |
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.
Vector containing transformed variable, distributed as standard normal.
Yurii Aulchenko
# 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) # tests with genetic data require(GenABEL.data) data(srdta) Zqt1 <- ztransform(qt1,srdta) Zqt1sexA <- ztransform(qt1~sex,srdta)