measurement
Levels of Measurement of Survey Items
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.
- Keywords
- manip
Usage
# S4 method for item
measurement(x)
# S4 method for item
measurement(x) <- value
# S4 method for data.set
measurement(x)
# S4 method for data.set
measurement(x) <- value
is.nominal(x)
is.ordinal(x)
is.interval(x)
is.ratio(x)
set_measurement(x,…)
Arguments
- x
an object, usually of class
"item"
.- value
for the
item
method, a character string; either "nominal", "ordinal", "interval", or "ratio"; for thedata.set
method, a list of character vectors with variable names, where the names of the list corresponds to a measurement level and and the list elements indicates the variables to which the measurement levels are assigned.- …
vectors of variable names, either symbols or character strings, tagged with the intended measurement level.
Value
The item
method of measurement(x)
returns a character
string, the data.set
method returns a named character vector,
where the name of each element is a variable name and each
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.
See Also
Examples
# NOT RUN {
vote <- sample(c(1,2,3,8,9),size=30,replace=TRUE)
labels(vote) <- c(Conservatives = 1,
Labour = 2,
"Liberal Democrats" = 3,
"Don't know" = 8,
"Answer refused" = 9
)
missing.values(vote) <- c(8,9)
as.data.frame(vote)[[1]]
measurement(vote) <- "interval"
as.data.frame(vote)[[1]]
group <- sample(c(1,2),size=30,replace=TRUE)
labels(group) <- c(A=1,B=2)
DataS <- data.set(group,vote)
measurement(DataS)
measurement(DataS) <- list(interval=c("group","vote"))
head(as.data.frame(DataS))
DataS <- set_measurement(DataS,
nominal=c(group,vote))
head(as.data.frame(DataS))
# }