itempool {irt}

Create an Itempool object

Description

This method creates a new Itempool-class object.

Usage

itempool(...)

Arguments

...

The object that is desired to be converted to an 'Itempool' object. Also additional arguments related to the Itempool.

Value

An Itempool-class object.

Author(s)

Emre Gonulates

Examples

# Create an item pool with two 2PL items
itempool(a = c(1, 1.4), b = c(-2, 1))
itempool(a = c(1, 1.4), b = c(-2, 1), model = "2PL")
# Set D parameter
itempool(a = c(1, 1.4), b = c(-2, 1), D = 1.7)
# Set item IDs
itempool(a = c(1, 1.4), b = c(-2, 1), item_id = c("i1", "i2"))
# Set content
itempool(a = c(1, 1.4), b = c(-2, 1), content = c("Algebra", "Geometry"))

# Create 3PL items from a data frame:
ipdf <- data.frame(a = c(.9, .79, 1.26),
                   b = c(-1, .43, -2.3),
                   c = c(.2, .38, .25))
itempool(ipdf)

# Create GRM (Graded Response Model) items from a data frame
ipdf <- data.frame(a = rlnorm(10, 0, .3), b1 = rnorm(10), b2 = rnorm(10))
itempool(ipdf, model = "GRM")

# Create a Rasch model item pool
itempool(b = c(-1, 0.2, 1.1), model = "Rasch")

# Add 'misc' field:
ip <- itempool(b = rnorm(2), item_id = paste0("t1-i", 1:2),
               misc = list(list(sympson_hetter_k = .8),
                           list(sympson_hetter_k = .9)))
ip[[1]]  # First item of the item pool