tradeoff.des {choiceDes} | R Documentation |

## MaxDiff and other tradeoff designs

### Description

Generate a design to be used for MaxDiff and related tradeoff exercises.

### Usage

```
tradeoff.des(items, shown, vers, tasks, fname=NULL, Rd=20, Rc=NULL, print=TRUE)
```

### Arguments

`items` |
The total number of items in the tradeoff exercise. |

`shown` |
The number of items shown in each tradeoff task. |

`vers` |
The number of blocks or versions in the final design. |

`tasks` |
The number of tradeoff tasks in |

`fname` |
A character string, usually ending in ".txt", indicating the name of the file containing the tradeoff design. |

`Rd` |
The number of iterations in the design and blocking processes. |

`Rc` |
The number of iterations in the item by column position optimization routine. |

`print` |
Boolean indicating whether there is output to the console during execution. |

### Details

Replicates the functionality of Sawtooth Software MaxDiff Designer for designing MaxDiff and related tradeoff tasks.

A modified Federov (1972) algorithm is applied to a factor equal in length to the number of items to optimize
the BIB design at `vers x tasks`

rows and `shown`

columns.

The optimized design is evaluated for one-way frequencies (equal representation of each item across all
versions and column positions). Designs are also optimized for two-way or pairwise balance across all tasks.
Column position balance is the more computationally-intensive process. The number of iterations required for
this step is determined by the `Rc`

argument which defaults to the larger of 1,000 or 10 `x`

the
number of rows in the design. Large design problems may require a larger number of iterations to achieve
optimal column position balance.

Once an optimal design has been found, it is blocked into versions using `optBlock`

to ensure equal
representation of items *within* each version. See Wheeler (2004) for a more complete description of the
modified Federov and blocking algorithms used in optimizing these designs.

If `fname`

is not `NULL`

a tab-delimited plain-text file is generated in the working
directory containing the levels-coded design.

### Value

`design` |
A matrix consisting of the optimized design and additional variables for card, version and task. |

`balance` |
Tables of one-way item frequencies, two-way (pairwise) item frequencies, and item frequencies by column position. Means and standard deviations are calculated from all elements of the one-way and column position tables, and from the off-diagonal elements of the two-way (pairwise) table. |

`Rc.crit` |
The criterion that is minimized to achieve column position balance is output as a vector
( |

`time.elapsed` |
The time required for the function to execute. |

### References

Federov, V.V. (1972). *Theory of optimal experiments.* Academic Press, New York.

Wheeler, R.E. (2004). *AlgDesign.* The R project for statistical computing.
(http://www.r-project.org).

### Examples

```
## Example 1:
## typical MaxDiff design with 12 items
des <- tradeoff.des(12, 4, 10, 9)
## Example 2:
## typical paired comparisons design with 14 items
des <- tradeoff.des(14, 2, 6, 14)
```

*choiceDes*version 0.9-3 Index]