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¶
## S4 method for signature 'item'
measurement(x)
## S4 method for signature 'item'
measurement(x) <- value
## S4 method for signature 'data.set'
measurement(x)
## S4 method for signature 'data.set'
measurement(x) <- value
is.nominal(x)
is.ordinal(x)
is.interval(x)
is.ratio(x)
set_measurement(x,...)
Arguments¶
xan object, usually of class
"item".valuefor the
itemmethod, a character string; either “nominal”, “ordinal”, “interval”, or “ratio”; for thedata.setmethod, 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.
See also¶
data.set, item
Examples¶
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]]
[1] Liberal Democrats Labour <NA> <NA> <NA>
[6] Conservatives Liberal Democrats Conservatives <NA> Conservatives
[11] Conservatives Conservatives Liberal Democrats Liberal Democrats <NA>
[16] <NA> <NA> Liberal Democrats Labour Labour
[21] Labour <NA> Liberal Democrats <NA> <NA>
[26] Labour Conservatives Liberal Democrats Conservatives Conservatives
Levels: Conservatives Labour Liberal Democrats
measurement(vote) <- "interval"
as.data.frame(vote)[[1]]
[1] 3 2 NA NA NA 1 3 1 NA 1 1 1 3 3 NA NA NA 3 2 2 2 NA 3 NA NA 2 1 3 1 1
group <- sample(c(1,2),size=30,replace=TRUE)
labels(group) <- c(A=1,B=2)
DataS <- data.set(group,vote)
measurement(DataS)
NULL
measurement(DataS) <- list(interval=c("group","vote"))
head(as.data.frame(DataS))
group vote
1 2 3
2 2 2
3 2 NA
4 2 NA
5 2 NA
6 2 1
DataS <- set_measurement(DataS,
nominal=c(group,vote))
head(as.data.frame(DataS))
group vote
1 B Liberal Democrats
2 B Labour
3 B <NA>
4 B <NA>
5 B <NA>
6 B Conservatives