WrightMap (version 1.4)

make.deltas: Calculate Master's Delta parameters.

Description

This function takes as its input a CQmodel object or the name of a ConQuest show file. It adds together the parameters as specified by the user, or if no tables are specified it reads the model equation to determine the appropriate tables to sum. This function is used by wrightMap to draw the item side of the map when a CQmodel is passed to wrightMap.

Usage

make.deltas(item.params, ...)
# S3 method for character
make.deltas(item.params, ...)
# S3 method for CQmodel
make.deltas(item.params, item.table = NULL, interactions = NULL, 
step.table = NULL, item.sign = NULL, inter.sign = NULL, 
	step.sign = NULL, ...)
# S3 method for default
make.deltas(item.params, cross.params = 0, step.params = 0, 
item.sign = 1, step.sign = 1, inter.sign = 1, ...)

Value

A matrix in which each row is an item and each column is a step

Arguments

item.params

The item parameters. Can either be a vector, a CQmodel object, or a path to a ConQuest show file

item.table

If item.params is a CQmodel object or a path to a ConQuest show file, item.table is the name of the items table. Commonly "item" but can be any string representing the name of a table in the ConQuest show file. This identifies what variable will form the rows of the delta matrix. If not specified, will be the first variable mentioned in the model equation.

interactions

If item.params is a CQmodel object or a path to a ConQuest show file, item.table is the name of the table with the interactions (if present). Commonly "item*step" but can be any string containing "*" that is the name of a table in the ConQuest show file. Should be the product of the item.table variable and the step.table variable (if present). If not specified, will be the product term of the model equation.

step.table

If item.params is a CQmodel object or a path to a ConQuest show file, step.table is the name of the steps table (if present). Commonly "step" but can be any string representing the name of a table in the ConQuest show file. This identifies what variable will form the columns of the delta matrix. If not specified, will be the second variable mentioned in the model equation.

item.sign

Can be 1 or -1. Indicates whether the item parameters should be added or subtracted.

inter.sign

Can be 1 or -1. Indicates whether the interaction parameters should be added or subtracted.

step.sign

Can be 1 or -1. Indicates whether the step parameters should be added or subtracted.

cross.params

If item.params is a vector, use this parameter to pass a matrix of interaction parameters.

step.params

If item.params is a vector, use this parameter to pass a matrix of step parameters.

...

Additional parameters

Author

Rebecca Freund & David Torres Irribarra

Details

This function reshapes the tables in the ConQuest show file and adds the step parameters to the appropriate items. The vector version of this is rarely called by the user.

See Also

make.thresholds CQmodel wrightMap

Examples

fpath <- system.file("extdata", package="WrightMap")

# Partial credit model
model1 <- CQmodel(file.path(fpath,"ex2a.eap"), file.path(fpath,"ex2a.shw")) 
make.deltas(model1)

# Rating scale model
model2 <- CQmodel(file.path(fpath,"ex2b.eap"), file.path(fpath,"ex2b-2.shw")) 
make.deltas(model2)

# Raters, criteria, topics
model3 <- CQmodel(file.path(fpath,"ex4a.mle"), file.path(fpath,"ex4a.shw")) 
make.deltas(model3, item.table = "rater")
make.deltas(model3, item.table = "rater", interactions = "rater*topic", step.table = "topic")