ltContrast: Calculate linear trend contrast coefficients.

In clayford/dvdata: Data Files for Design and Analysis of Experiments (Dean & Voss)

Calculate linear trend contrast coefficients.

Description

Calculates linear trend contrast coefficients according to 4.2.4.

Usage

ltContrast(f)

Arguments

f

A factor.

Examples

# example 4.23
is.factor(heartlung.pump$RPM) # TRUE
ltc <- ltContrast(heartlung.pump$RPM)
afr <- with(heartlung.pump, tapply(Y,RPM, mean))
# least squares estimate of linear contrast:
crossprod(afr,ltc)
# get msE:
lmHL <- lm(Y ~ RPM, heartlung.pump)
msE <- summary(lmHL)$sigma^2
# estimated standard error of the linear trend estimator:
sqrt(msE * sum(ltc^2/table(heartlung.pump$RPM)))

clayford/dvdata documentation built on June 11, 2025, 8:43 a.m.