1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
\name{subset.itemresp}
\alias{subset.itemresp}
\alias{merge.itemresp}
\alias{c.itemresp}
\alias{[.itemresp}
\title{Subsetting Item Response Data}
\description{
Subsetting and combining \code{"itemresp"} data objects.
}
\usage{
\method{subset}{itemresp}(x, items = NULL, subjects = NULL, \dots)
}
\arguments{
\item{x}{an object of class \code{"itemresp"}.}
\item{items}{character, integer, or logical for subsetting the items.}
\item{subjects}{character, integer, or logical for subsetting the subjects.}
\item{\dots}{currently not used.}
}
\details{
The \code{subset} method selects subsets of items and/or subjects in
item response data. Alternatively, the \code{[} method can be used
with the row index corresponding to subjects and the column index
corresponding to items.
The \code{c} method can be used to combine item response data from
different subjects for the same items
The \code{merge} method can be used to combine item response data
from the same subjects for different items.
}
\seealso{\code{\link{itemresp}}}
\examples{
## binary responses to three items, coded as matrix
x <- cbind(c(1, 0, 1, 0), c(1, 0, 0, 0), c(0, 1, 1, 1))
xi <- itemresp(x)
## subsetting/indexing
xi[2]
xi[-(3:4)]
xi[c(TRUE, TRUE, FALSE, FALSE)]
subset(xi, items = 1:2) # or xi[, 1:2]
subset(xi, items = -2, subjects = 2:3)
## combine two itemresp vectors for different subjects but the same items
xi12 <- xi[1:2]
xi34 <- xi[3:4]
c(xi12, xi34)
## combine two itemresp vectors for the same subjects but different items
## polytomous responses in a data frame
d <- data.frame(q1 = c(-2, 1, -1, 0), q2 = factor(c(1, 3, 1, 3),
levels = 1:3, labels = c("disagree", "neutral", "agree")))
di <-itemresp(d)
merge(xi, di)
## if subjects have names/IDs, these are used for merging
names(xi) <- c("John", "Joan", "Jen", "Jim")
names(di) <- c("Joan", "Jen", "Jim", "Jo")
merge(xi, di)
merge(xi, di, all = TRUE)
}
\keyword{classes}
|
