item.reverse: Reverse Code Scale Item

Description

This function reverse codes inverted items, i.e., items that are negatively worded.

Usage

item.reverse(data, ..., min = NULL, max = NULL, keep = NULL, append = TRUE,
             name = ".r", as.na = NULL, table = FALSE, check = TRUE)

Value

Returns a numeric vector or data frame with the same length or same number of rows as data containing the reverse coded scale item(s).

Arguments

data: a numeric vector for reverse coding an item or data frame for reverse coding more than one item.
...: an expression indicating the variable names in data e.g., item.reverse(x1, x2, x3, data = dat). Note that the operators ., +, -, ~, :, ::, and ! can also be used to select variables, see 'Details' in the df.subset function.
min: an integer indicating the minimum of the item (i.e., lowest possible scale value).
max: an integer indicating the maximum of the item (i.e., highest possible scale value).
keep: a numeric vector indicating values not to be reverse coded.
append: logical: if TRUE (default), recoded variable(s) are appended to the data frame specified in the argument data.
name: a character string or character vector indicating the names of the reverse coded item. By default, variables are named with the ending ".r" resulting in e.g. "x1.r" and "x2.r". Variable names can also be specified using a character vector matching the number of variables (e.g., name = c("reverse.x1", "reverse.x2")).
as.na: a numeric vector indicating user-defined missing values, i.e. these values are converted to NA before conducting the analysis.
table: logical: if TRUE, a cross table item x reverse coded item is printed on the console if only one variable is specified.
check: logical: if TRUE (default), argument specification is checked.

Author

Takuya Yanagida takuya.yanagida@univie.ac.at

Details

If arguments min and/or max are not specified, empirical minimum and/or maximum is computed from the data Note, however, that reverse coding might fail if the lowest or highest possible scale value is not represented in the data That is, it is always preferable to specify the arguments min and max.

References

Rasch, D., Kubinger, K. D., & Yanagida, T. (2011). Statistics in psychology - Using R and SPSS. John Wiley & Sons.

Examples

Run this code

dat <- data.frame(item1 = c(1, 5, 3, 1, 4, 4, 1, 5),
                  item2 = c(1, 1.3, 1.7, 2, 2.7, 3.3, 4.7, 5),
                  item3 = c(4, 2, 4, 5, 1, 3, 5, -99))

# Example 1: Reverse code 'item1' and append to 'dat'
item.reverse(dat, item1, min = 1, max = 5)

# Alternative specification without using the '...' argument
item.reverse(dat$item1, min = 1, max = 5)

# Example 2: Reverse code 'item3' while keeping the value -99
item.reverse(dat, item3, min = 1, max = 5, keep = -99)

# Example 3: Reverse code 'item3' while keeping the value -99 and check recoding
item.reverse(dat, item3, min = 1, max = 5, keep = -99, table = TRUE)

# Example 4: Reverse code 'item1', 'item2', and 'item3' and attach to 'dat'
item.reverse(item1:item3, data = dat, min = 1, max = 5, keep = -99)

# Alternative specification without using the '...' argument
dat <- cbind(dat,
             item.reverse(dat[, c("item1", "item2", "item3")],
                          min = 1, max = 5, keep = -99))

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