Description Usage Arguments Details Value Author(s) References See Also

This function combines objects of class `irt.pars`

and/or
`sep.pars`

into a single `irt.pars`

object

1 | ```
combine.pars(x, common, grp.names)
``` |

`x` |
an ordered list containing two or more |

`common` |
an n x 2 matrix or list of matrices identifying the common items between
adjacent pairs of objects in |

`grp.names` |
character vector of names for all the groups in the returned object |

Although many of the methods in this package allow for lists containing `irt.pars`

and `sep.pars`

objects, it may be helpful to combine the item parameters for multiple
groups into a single object. `x`

can include a combination of `irt.pars`

and
`sep.pars`

objects. The `irt.pars`

objects can contain information for a
single group or multiple groups. The list elements in `x`

should be ordered such that
adjacent elements correspond to adjacent groups. If an `irt.pars`

object is included
with multiple groups, the list element following this object should contain information for a
group that is adjacent to the last group in the `irt.pars`

object.

If `x`

contains only two elements, `common`

should be a matrix. If `x`

contains
more than two elements, `common`

should be a list. In any of the `common`

matrices
the first column identifies the common items for the first group of two adjacent list elements
in `x`

. The second column in `common`

identifies the corresponding set of common
items from the next list element in `x`

. For example, if `x`

contains only two list
elements, a single set of common items links them together. If item 4 in group one (row 4 in
slot `pars`

) is the same as item 6 in group two, the first row of `common`

would be `"4,6"`

.

If an `irt.pars`

object is included with multiple groups, `common`

should correspond
to the set of common items between the last group in the `irt.pars`

object and the
group in the adjacent element in `x`

.

Returns an object of class `irt.pars`

Jonathan P. Weeks weeksjp@gmail.com

Weeks, J. P. (2010)
**plink**: An R package for linking mixed-format tests using IRT-based methods.
*Journal of Statistical Software*, **35(12)**, 1–33.
URL http://www.jstatsoft.org/v35/i12/

`irt.pars`

, `as.irt.pars`

, `sep.pars`

,
`sep.pars`

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