graphics {irtProb} | R Documentation |
Graphic functions to illustrate response curves and parameter estimation.
PCC(theta = 0, S = 0, C = 0, D = 0, s = 1/1.702, b = seq(-5, 5, length = 300), c = 0, d = 1, groups = TRUE, ID = "ID", main = "Person Characteristic Curve", xlab = "Item Difficulty Parameter (b)", ylab = "P(x = 1)", type = c("g", "a"))
theta |
numeric; vector of person proficiency (theta) levels scaled on a normal z score. |
S |
numeric: positive vector of personal fluctuation parameters (σ). |
C |
numeric: positive vector of personal pseudo-guessing parameters (chi, a probability between 0 and 1). |
D |
numeric: positive vector of personal inattention parameters (delta, a probability between 0 and 1). |
s |
numeric: vector of item fluctuation parameter or the inverse of item discrimination (s= 1/a). |
b |
numeric: vector of item discrimination parameter. |
c |
numeric: vector of item pseudo-guessing parameter. |
d |
numeric: vector of item inattention parameter. |
ID |
character: curves identification information displayed ("ID", "ALL", "THETA2 or NULL) |
groups |
logical: default to TRUE . If TRUE , Lattice xyplot by groups.
If FALSE , xyplot with shingles. |
main |
character: first line of main title. |
xlab |
character: label of x axis. |
ylab |
character: label of y axis. |
type |
character: type of xyplot graphic. One of the following:
"p", "l", "h", "b", "o", "s", "S", "r", "a", "g", "smooth". |
PCC
returns a list:
graphic |
trellis object: figures for each subject (group or shingle representation). |
probability |
data.frame: item snd person parameters, like th eprobability of a correct response. |
Gilles Raiche, Universite du Quebec a Montreal (UQAM),
Departement d'education et pedagogie
Raiche.Gilles@uqam.ca, http://www.er.uqam.ca/nobel/r17165/
## PCC curves grouped on a single figure res1 <- PCC(theta=c(-2,-2,-2),S=0, C=c(0.0, 0.1, 0.6), D=0.2, b=seq(-5,5,length=3000), ID=NULL, groups=TRUE, type=c("g","a")) res1 ## PCC curves shingled on a single figure for each subject res2 <- PCC(theta=c(-2,-1,0),S=c(4.0,0.0, 1.0), C=c(0.0, 0.1, 0.6), D=0.2, b=seq(-5,5,length=3000), ID=NULL, groups=FALSE, type=c("g","a")) res2