Subsetting Item Response Data
Subsetting and combining "itemresp" data objects.
## S3 method for class 'itemresp' subset(x, items = NULL, subjects = NULL, ...)
x |
an object of class |
items |
character, integer, or logical for subsetting the items. |
subjects |
character, integer, or logical for subsetting the subjects. |
... |
currently not used. |
The subset method selects subsets of items and/or subjects in
item response data. Alternatively, the [ method can be used
with the row index corresponding to subjects and the column index
corresponding to items.
The c method can be used to combine item response data from
different subjects for the same items
The merge method can be used to combine item response data
from the same subjects for different items.
## 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)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.