R: Subsetting Item Response Data

subset.itemresp {psychotools} | R Documentation

## Subsetting Item Response Data

### Description

Subsetting and combining `"itemresp"` data objects.

### Usage

      ## S3 method for class 'itemresp'
    subset(x, items = NULL, subjects = NULL, ...)

### Arguments

`x` | an object of class `"itemresp"`.
`items` | character, integer, or logical for subsetting the items.
`subjects` | character, integer, or logical for subsetting the subjects.
`...` | currently not used.

### Details

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.

### See Also

`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)

[Package psychotools version 0.4-2 Index]