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]