plotCRC {GGUM}

Plot item category response curves (CRCs)

Description

plot.CRC plots item CRCs for the GUM and the GGUM.

Usage

plotCRC(IP, items = NULL, x.lim = 4, ThetaminDelta = TRUE, quiet = FALSE)

Arguments

IP

Object of class GGUM.

items

Vector indicating the items for which the CRCs are to be plotted. Default is all items.

x.lim

Controls the limits of the x-axis. Default is -4 through +4.

ThetaminDelta

Logical; if TRUE, plot the CRCs centered at 0, otherwise plot the CRCs centered at \delta (item's difficulty). Default is TRUE.

quiet

Render all plots for items at once? Default is FALSE.

Value

The function returns a three-dimensional array with the probabilities associated to each item's CRC. These are the values shown in the plot.

Details

This function plots the item category response curves (CRCs) for the requested items.

Author(s)

Jorge N. Tendeiro, [e-mail]

Examples

# For GUM:
# Generate data:
gen1 <- GenData.GGUM(400, 5, 3, "GUM", seed = 139)
# Fit the GUM:
fit1 <- GUM(gen1$data, 3)
# Plot CRCs:
plotCRC(fit1, items = 1, quiet = TRUE)
## Not run: 
# For GGUM:
# Generate data:
set.seed(1); C <- sample(3:5, 10, replace = TRUE)
gen2 <- GenData.GGUM(2000, 10, C, "GGUM", seed = 156)
# Fit the GGUM:
fit2 <- GGUM(gen2$data, C)
# Plot CRCs:
plotCRC(fit2, items = 1, quiet = TRUE)

## End(Not run)