# sequences: Obtain sequences for BE study designs In randomizeBE: Create a Random List for Crossover Studies

## Description

The function is intended as helper function to get the sequences for commonly used designs in BE studies.
These sequences may then subsequently used in function `RL4()`.

## Usage

 `1` ```sequences(design, tmts = NULL) ```

## Arguments

 `design` A character value describing the study design. For crossover studies it is "tmts x sequences x periods" without space. F.i. "2x2x2" is the standard 2-treatments-2-sequence-2-period crossover. The designs `"2x2x2", "3x3x3", "4x4x4"` may be abbreviated to `"2x2", "3x3", "4x4"`. `tmts` A character vector with the codes of the treatments.

## Details

This function was implemented because I couldn't remember f.i. all the six sequences of a "3x6x3" design if had to be coded by T1,T2 and R.
The sequences are primarily build within the ABC... notation.
If treatment codes are given the "AB..." in the sequences are replaced by these codes.

The following designs are implemented:
`"parallel"` = 2-group parallel design
`"2x2"` = classical 2-treatments-2-sequence-2-period crossover
`"3x3"` = 3-treatments-3-sequence-3-period crossover (Latin square)
`"3x6x3"` = 3-treatments-6-sequence-3-period crossover (Williams design)
`"4x4"` = 4-treatments-4-sequence-4-period crossover (Latin square)
`"2x2x3"` = 2-sequence-3-period replicate crossover
`"2x2x4"` = 2-sequence-4-period full replicate crossover
`"2x4x4"` = 4-sequence-4-period full replicate crossover
`"2x3x3"` = 3-sequence-3-period partial (reference) replicate crossover
`"2x4x2"` = 4-sequence-2-period replicate crossover, Baalams design.

The sequences for the `"3x3"` and `"4x4"` designs are randomly derived from the standard Latin squares (in ABC notation)
`ABC, BCA, CAB`
or in case of the `"4x4"` design from
`ABCD, BDAC, CADB, DCBA`.

## Value

Returns a character vector with the sequences.

## Note

For the higher order designs (designs with more than 2 treatments or replicate crossover designs, respectively) only a selection of possible designs are covered.
The design sequences for `"4x4"` are not guaranteed to be a Williams design. If need a Williams design use function `williams()` instead.

Detlew Labes

## References

Jones B, Kenward MG (2003). "Design and Analysis of Cross-Over Trials" 2nd edition. Chapman & Hall, London.

`williams`, `RL4`

## Examples

 ```1 2 3 4 5 6 7 8``` ```# classical 2x2 crossover in TR notation (simple enough to remember sequences("2x2", tmts=c("T","R")) # 3-treatment-6-sequence-3-period Williams design in ABC notation sequences("3x6x3") # 3-treatment-3-sequence-3-period design with one Test and two References sequences("3x3", tmts=c("T","R1","R2")) # 4-treatment-4-period in TxRy notation, two Test and two Reference sequences("4x4", tmts=c("T1","T2","R1","R2")) ```

### Example output

```[1] "TR" "RT"
[1] "ABC" "BCA" "CAB" "ACB" "BAC" "CBA"
[1] "TR2R1" "R1TR2" "R2R1T"
[1] "T1R1R2T2" "T2T1R1R2" "R1R2T2T1" "R2T2T1R1"
```

randomizeBE documentation built on June 20, 2018, 5:01 p.m.