measurement: Levels of Measurement of Survey Items

Description

The measurement level of a "item" object, which is one of "nominal", "ordinal", "interval", "ratio", determines what happens to it, if it or the data.set containing it is coerced into a data.frame. If the level of measurement level is "nominal", the it will be converted into an (unordered) factor, if the level of measurement is "ordinal", the item will be converted into an ordered vector. If the measurement is "interval" or "ratio", the item will be converted into a numerical vector.

Usage

## S3 method for class 'item':
measurement(x)
## S3 method for class 'item':
measurement(x) <- value
is.nominal(x)
is.ordinal(x)
is.interval(x)
is.ratio(x)

Arguments

an object, usually of class "item".

value

a character string; either "nominal", "ordinal", "interval", or "ratio".

Value

measurement(x) returns a character string. is.nominal, is.ordinal, is.interval, is.ratio return a logical value.

References

Stevens, Stanley S. 1946. "On the theory of scales of measurement." Science 103: 677-680.

Examples

Run this code

answer <- sample(c(1,2,3,8,9),size=30,replace=TRUE)
labels(answer) <- c(Conservatives         =  1,
                    Labour                =  2,
                    "Liberal Democrats"   =  3,
                    "Don't know"          =  8,
                    "Answer refused"      =  9
                    )
missing.values(answer) <- c(8,9)
as.data.frame(answer)[[1]]
measurement(answer) <- "interval"
as.data.frame(answer)[[1]]