make.thresholds: Calculate Thurstonian thresholds.

Description Usage Arguments Value Author(s) See Also Examples

View source: R/make.thresholds.R

Description

This function accepts a matrix of delta parameters and converts them to thresholds (using a threshold of .5). It can also take as input a CQmodel object or a filename of a ConQuest show file.

Usage

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make.thresholds(item.params, ...)
## S3 method for class 'character'
make.thresholds(item.params, design.matrix = "normal",...)
## S3 method for class 'CQmodel'
make.thresholds(item.params,item.table = NULL, interactions = NULL
,step.table = NULL, design.matrix = "normal", throld = 0.5, alpha = 1,...)
## Default S3 method:
make.thresholds(item.params, design.matrix = "normal"
, make.from = "deltas", theta.interval = c(-10, 10), throld = 0.5, alpha = 1
, c.params = 0,...)
## S3 method for class 'matrix'
make.thresholds(item.params, design.matrix = "normal"
, make.from = "deltas", theta.interval = c(-10, 10), throld = 0.5
, alpha = 1, c.params = 0,...)

Arguments

item.params

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

design.matrix

Can be "normal" or "ConQuest". Note that for a CQmodel object or ConQuest file, should be normal, NOT ConQuest.

make.from

Specifies whether the item.params matrix contains threshold or delta parameters.

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 thresholds 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 thresholds matrix. If not specified, will be the second variable mentioned in the model equation.

theta.interval

If item.params is a matrix, theta.interval specifies over what interval to search for the parameters.

throld

The probability level to use for calculating the thresholds.

alpha

A vector or single value for the slope parameter or parameters.

c.params

A vector or single value for the guessing parameter or parameters.

...

Additional parameters.

Value

A matrix of threshold parameters.

Author(s)

Daniel Coulter Furr, Rebecca Freund, & David Torres Irribarra

See Also

make.deltas itemData CQmodel wrightMap

Examples

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

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

Example output

Assuming partial credit model
                    [,1]       [,2]       [,3]
Earth shape   -1.3229164 -0.1310804         NA
Earth pictu.. -0.9241595  0.4451567  2.7832333
Falling off   -1.4503041  1.3141486  1.9728871
What is Sun   -1.0466830  1.4306938         NA
Moonshine     -0.6759150 -0.2252513  0.4156190
Moon and ni.. -0.8076978  1.0336795         NA
Night and d.. -0.6343026 -0.1937096  0.1852925
Breathe on .. -0.7007363 -0.5078997 -0.4741583
Assuming partial credit model
                    [,1]       [,2]       [,3]
Earth shape   -1.3229164 -0.1310804         NA
Earth pictu.. -0.9241595  0.4451567  2.7832333
Falling off   -1.4503041  1.3141486  1.9728871
What is Sun   -1.0466830  1.4306938         NA
Moonshine     -0.6759150 -0.2252513  0.4156190
Moon and ni.. -0.8076978  1.0336795         NA
Night and d.. -0.6343026 -0.1937096  0.1852925
Breathe on .. -0.7007363 -0.5078997 -0.4741583

WrightMap documentation built on May 1, 2019, 8:18 p.m.