growthcurve {statmod}R Documentation

Compare Groups of Growth Curves

Description

Do all pairwise comparisons between groups of growth curves using a permutation test.

Usage

compareGrowthCurves(group,y,levels=NULL,nsim=100,fun=meanT,times=NULL,verbose=TRUE,adjust="holm")
compareTwoGrowthCurves(group,y,nsim=100,fun=meanT)

Arguments

group vector or factor indicating group membership. Missing values are allowed in compareGrowthCurves but not in compareTwoGrowthCurves.
y matrix of response values with rows for individuals and columns for times. The number of rows must agree with the length of group. Missing values are allowed.
levels a character vector containing the identifiers of the groups to be compared. By default all groups with two more more members will be compared.
nsim number of permutations to estimated p-values.
fun the statistic used to measure the distance between two groups of growth curves. Default to a mean t-statistic.
times a numeric vector containing the column numbers on which the groups should be compared. By default all the columns are used.
verbose should progress results be printed?
adjust method used to adjust for multiple testing, see p.adjust.

Details

compareTwoGrowthCurves performs a permutation test of the difference between two groups of growth curves. compareGrowthCurves does all pairwise comparisons between two or more groups of growth curves. Accurate p-values can be obtained by setting nsim to some large value, nsim=10000 say.

Value

compareTwoGrowthCurves returns a list with two components, stat and p.value, containing the observed statistics and the estimated p-value. compareGrowthCurves returns a data frame with components

Group1 name of first group in a comparison
Group2 name of second group in a comparison
Stat observed value of the statistic
P.Value estimated p-value
adj.P.Value p-value adjusted for multiple testing

Author(s)

Gordon Smyth

See Also

compareGrowthCurves, compareTwoGrowthCurves

Examples

# A example with only one time
data(PlantGrowth)
compareGrowthCurves(PlantGrowth$group,as.matrix(PlantGrowth$weight))
# Can make p-values more accurate by nsim=10000

[Package statmod version 1.2.4 Index]