View source: R/acrossFormsConstraint.R
acrossFormsConstraint | R Documentation |
Create constraints related to item values. That is, the created
constraints assure that the sum of the item values (itemValues
) across test forms is either
(a) smaller than or equal to (operator = "<="
), (b) equal to
(operator = "="
), or (c) greater than or equal to (operator = ">="
)
the chosen targetValue
. Note that the length of itemValues
should
equal to the number of the length of whichForms
times whichItems
.
acrossFormsConstraint( nForms, nItems = NULL, operator = c("<=", "=", ">="), targetValue, whichForms = seq_len(nForms), whichItems = NULL, itemIDs = NULL, itemValues = NULL, info_text = NULL )
nForms |
Number of forms to be created. |
nItems |
Number of items in the item pool [optional to create |
operator |
A character indicating which operator should be used in the
constraints, with three possible values: |
targetValue |
the target value. The target sum of item values across test forms. |
whichForms |
An integer vector indicating across which test forms the sum should constrained. Defaults to all the test forms. |
whichItems |
A vector indicating which items should be constrained. Defaults to all the items. |
itemIDs |
a character vector of item IDs in correct ordering, or NULL. |
itemValues |
a vector of item values for which the sum across test forms should be constrained. The item values will be repeated for each form. Defaults to a vector with ones for all items in the pool. |
info_text |
a character string of length 1, to be used in the |
An object of class "constraint"
.
## constraints to make sure that accross test form 1 and 3, only 4 items ## of items 1:10 appear. Note that the constraint should be used in ## in combination with constraining item overlap between the forms. constr1 <- combineConstraints( acrossFormsConstraint(nForms = 3, operator = "=", targetValue = 4, whichForms = c(1, 3), itemValues = c(rep(1, 10), rep(0, 10)), itemIDs = 1:20), itemUsageConstraint(nForms = 3, nItems = 20, operator = "=", targetValue = 1, itemIDs = 1:20) ) ## or alternatively constr2 <- combineConstraints( acrossFormsConstraint(nForms = 3, nItems = 20, operator = "=", targetValue = 4, whichForms = c(1, 3), whichItems = 1:10, itemIDs = 1:20), itemUsageConstraint(nForms = 3, nItems = 20, operator = "=", targetValue = 1, itemIDs = 1:20) )
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