Convert to Numeric via Factor

Converts an object to numeric by first coercing it to a factor and then to numeric. This is useful whenever a categorical or character variable needs a purely numeric stand-in – for example, as input to functions that require numeric data (distance calculations, correlation matrices, some modelling routines), or to obtain a compact, deterministic small-integer code for an ordinal variable by passing an explicit levels order.

Usage

nf(x, ...)

Arguments

x

a vector to be converted.

...

additional arguments passed to factor().

Value

a numeric vector corresponding to the integer codes of the factor levels.

Details

This function is a shorthand for as.numeric(factor(x, ...)).

Note that the resulting numeric values correspond to the internal factor levels, not the original numeric values. In particular, for character vectors holding numbers the codes follow the alphabetical level order (see the last example) – use as.numeric(as.character(x)) to recover the values themselves.

See also

factor(), as.numeric()

Other data.recode: asBinary(), combLevels(), dummy(), mReplace(), recodeX(), revCode(), stringsAsFactors()

Examples

nf(c("a", "b", "a"))
#> [1] 1 2 1
nf(c("low", "medium", "high"), levels = c("low", "medium", "high"))
#> [1] 1 2 3

# caution: codes, not values
nf(c("10", "2"))    # 1 2, not 10 2
#> [1] 1 2