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Factor As Numeric

fct_to_num.Rd

Transform a factor to approximately its original numeric values.

Usage

fct_to_num(f)

Arguments

f

factor to be converted to numeric values

Value

Numeric

Details

See ‘Warning’ section of factor: –

“In particular, as.numeric applied to a factor is meaningless, and may happen by implicit coercion. To transform a factor f to approximately its original numeric values, as.numeric(levels(f))[f] is recommended and slightly more efficient than as.numeric(as.character(f)).”

Accordingly, fct_to_num() implements this method.

See also

factor

Examples

## Create sequence of numeric values as a factor
(f <- factor(2001:2020))
#>  [1] 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
#> [16] 2016 2017 2018 2019 2020
#> 20 Levels: 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 ... 2020

## Seemingly numeric levels are actually character strings!
levels(f) |> str()
#>  chr [1:20] "2001" "2002" "2003" "2004" "2005" "2006" "2007" "2008" "2009" ...

## Returns codes for factor levels, not what was expected
f |> as.numeric()
#>  [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20

## Returns numeric values equivalent to factor levels
f |> fct_to_num()
#>  [1] 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
#> [16] 2016 2017 2018 2019 2020

rm(f)