plot.info {irtQ} | R Documentation |
Plot Item and Test Information Functions
Description
This method plots item or test information functions for a specified set of theta values. It can also display the conditional standard error of estimation (CSEE) at the test level.
Usage
## S3 method for class 'info'
plot(
x,
item.loc = NULL,
overlap = FALSE,
csee = FALSE,
xlab.text,
ylab.text,
main.text,
lab.size = 15,
main.size = 15,
axis.size = 15,
line.color,
line.size = 1,
layout.col = 4,
strip.size = 12,
...
)
Arguments
x |
x An object of class |
item.loc |
A numeric vector indicating which item information functions to plot,
specified by item position (e.g., 1 for the first item). If |
overlap |
Logical. If |
csee |
Logical. If |
xlab.text , ylab.text |
Character strings specifying the labels for the x and y axes, respectively. |
main.text |
Character string specifying the overall title of the plot. |
lab.size |
Numeric value specifying the font size of axis titles. Default is 15. |
main.size |
Numeric value specifying the font size of the plot title. Default is 15. |
axis.size |
Numeric value specifying the font size of axis tick labels. Default is 15. |
line.color |
A character string specifying the color of the plot lines. See http://www.cookbook-r.com/Graphs/Colors_(ggplot2)/ for available color names. |
line.size |
Numeric value specifying the thickness of plot lines. Default is 1. |
layout.col |
Integer. Number of columns to use when faceting multiple
item information functions. Used only when |
strip.size |
Numeric value specifying the font size of facet labels when multiple items are displayed. |
... |
Additional arguments passed to |
Details
All of the plots are drawn using the ggplot2 package. The
object of class info
can be obtained from the function info()
.
Value
This method function displays the item or test information function
plot. When csee = TRUE
, the CSEE is returned at the test level.
Author(s)
Hwanggyu Lim hglim83@gmail.com
See Also
Examples
## Example using a "-prm.txt" file exported from flexMIRT
# Import the "-prm.txt" output file from flexMIRT
flex_prm <- system.file("extdata", "flexmirt_sample-prm.txt", package = "irtQ")
# Read the item parameters and convert them to item metadata
test_flex <- bring.flexmirt(file = flex_prm, "par")$Group1$full_df
# Define a sequence of theta values
theta <- seq(-4, 4, 0.1)
# Compute item and test information values for the given theta values
x <- info(x = test_flex, theta = theta, D = 1, tif = TRUE)
# Plot the test information function
plot(x)
# Plot the item information function for the second item
plot(x, item.loc = 2)
# Plot multiple item information functions, each in a separate panel
plot(x, item.loc = 1:8, overlap = FALSE)
# Plot multiple item information functions in a single panel
plot(x, item.loc = 1:8, overlap = TRUE)
# Plot the conditional standard error of estimation (CSEE) at the test level
plot(x, csee = TRUE)