irf {bggum}  R Documentation 
Plots response functions given alpha, delta, and tau parameters.
irf(a, d, t, from = 3, to = 3, by = 0.01, layout_matrix = 1, main_title = "Item Response Function", sub = "", option_names = NULL, line_types = NULL, color = "black", rug = FALSE, thetas = NULL, responses = NULL, sides = 1, rug_colors = "black")
a 
A numeric vector of alpha parameters 
d 
A numeric vector of delta parameters 
t 
Either a list of numeric vectors for the tau parameters for each option, or a numeric vector if the IRF for only one item is desired – note the first element of each vector should be zero 
from 
A numeric vector of length one, the lowest theta value to estimate response probabilities for; default is 3 
to 
A numeric vector of length one, the highest theta value to estimate response probabilities for; default is 3 
by 
A numeric vector of length one giving the spacing between theta values; default is 0.01 
layout_matrix 
An integer matrix dictating the layout of the plot; the default is a onecolumn matrix with one element for each item 
main_title 
A character vector giving the plots' main titles; default is "Item Response Function". 
sub 
An optional character vector of subtitles for the resulting plots, to be pasted onto the main title (helpful for titling individual plots when plotting multiple items' IRFs). 
option_names 
An optional character vector giving names for the items' options; if NULL, generic names (e.g. "Option 1", "Option 2", etc.) are used 
line_types 
An optional integer vector specifying lty for each option; if not provided, the first option for each question will have lty = 1, the second will have lty = 2, etc. 
color 
A specification of the colors to draw lines in. Colors can be
specified by either a character vector of colors (either names that R
recognizes or hexidecimal specifications) or a function taking a single
argument for the number of colors to return. See

rug 
A logical vector of length one specifying whether to draw a rug of theta estimates; the default is FALSE 
thetas 
An optional vector of theta estimates for rug drawing;
if 
responses 
An optional matrix or vector (if the IRF for only one item
is desired) of responses; if 
sides 
A vector giving the side(s) to draw the rug on if

rug_colors 
A vector giving the color(s) to draw the rug in if

## We'll simulate data to use for these examples: set.seed(123) sim_data < ggum_simulation(100, 10, 4) ## You can plot the IRF for one item: irf(sim_data$alpha[1], sim_data$delta[1], sim_data$tau[[1]], option_names = 0:3) ## Or multiple items: irf(sim_data$alpha[1:2], sim_data$delta[1:2], sim_data$tau[1:2], option_names = 0:3, sub = 1:2) ## You can plot it in color: irf(sim_data$alpha[1], sim_data$delta[1], sim_data$tau[[1]], option_names = 0:3, color = tango) ## You can also plot a rug of the repsondents' theta estimates with the IRF irf(sim_data$alpha[1], sim_data$delta[1], sim_data$tau[[1]], rug = TRUE, responses = sim_data$response_matrix[ , 1], thetas = sim_data$theta, option_names = 0:3)