as_numeric {sjlabelled}

Convert factors to numeric variables

Description

This function converts (replaces) factor levels with the related factor level index number, thus the factor is converted to a numeric variable.

Usage

as_numeric(x, ...)

to_numeric(x, ...)

## S3 method for class 'data.frame'
as_numeric(x, ..., start.at = NULL, keep.labels = TRUE, use.labels = FALSE)

Arguments

x

A vector or data frame.

...

Optional, unquoted names of variables that should be selected for further processing. Required, if x is a data frame (and no vector) and only selected variables from x should be processed. You may also use functions like : or tidyselect's select-helpers. See 'Examples'.

start.at

Starting index, i.e. the lowest numeric value of the variable's value range. By default, this argument is NULL, hence the lowest value of the returned numeric variable corresponds to the lowest factor level (if factor levels are numeric) or to 1 (if factor levels are not numeric).

keep.labels

Logical, if TRUE, former factor levels will be added as value labels. For numeric factor levels, values labels will be used, if present. See 'Examples' and set_labels for more details.

use.labels

Logical, if TRUE and x has numeric value labels, the values defined in the labels (right-hand side of labels, for instance labels = c(null = 0, one = 1)) will be set as numeric values (instead of consecutive factor level numbers). See 'Examples'.

Value

A numeric variable with values ranging either from start.at to start.at + length of factor levels, or to the corresponding factor levels (if these were numeric). If x is a data frame, the complete data frame x will be returned, where variables specified in ... are coerced to numeric; if ... is not specified, applies to all variables in the data frame.

Examples

data(efc)
test <- as_label(efc$e42dep)
table(test)

table(as_numeric(test))
hist(as_numeric(test, start.at = 0))

# set lowest value of new variable to "5".
table(as_numeric(test, start.at = 5))

# numeric factor keeps values
dummy <- factor(c("3", "4", "6"))
table(as_numeric(dummy))

# do not drop unused factor levels
dummy <- ordered(c(rep("No", 5), rep("Maybe", 3)),
                 levels = c("Yes", "No", "Maybe"))
as_numeric(dummy)

# non-numeric factor is converted to numeric
# starting at 1
dummy <- factor(c("D", "F", "H"))
table(as_numeric(dummy))

# for numeric factor levels, value labels will be used, if present
dummy1 <- factor(c("3", "4", "6"))
dummy1 <- set_labels(dummy1, labels = c("first", "2nd", "3rd"))
dummy1
as_numeric(dummy1)

# for non-numeric factor levels, these will be used.
# value labels will be ignored
dummy2 <- factor(c("D", "F", "H"))
dummy2 <- set_labels(dummy2, labels = c("first", "2nd", "3rd"))
dummy2
as_numeric(dummy2)


# easily coerce specific variables in a data frame to numeric
# and keep other variables, with their class preserved
data(efc)
efc$e42dep <- as.factor(efc$e42dep)
efc$e16sex <- as.factor(efc$e16sex)
efc$e17age <- as.factor(efc$e17age)

# convert back "sex" and "age" into numeric
head(as_numeric(efc, e16sex, e17age))

x <- factor(c("None", "Little", "Some", "Lots"))
x <- set_labels(x,
  labels = c(None = "0.5", Little = "1.3", Some = "1.8", Lots = ".2")
)
x
as_numeric(x)
as_numeric(x, use.labels = TRUE)
as_numeric(x, use.labels = TRUE, keep.labels = FALSE)