[R] [as.numeric]Convert Category data to Numeric Data

arun
Mon, 03 Feb 2014 01:07:27 -0000

Hi,
as.numeric(iris$Species)


iris1 <- within(iris,Species <-as.numeric(Species))
A.K.


I have a small question for converting the category data to numeric data.

For example, if we use the iris data in r. we have:

str(iris)
'data.frame':	150 obs. of ?5 variables:
?$ Sepal.Length: num ?5.1 4.9 4.7 4.6 5 5.4 4.6 5 4.4 4.9 ...
?$ Sepal.Width : num ?3.5 3 3.2 3.1 3.6 3.9 3.4 3.4 2.9 3.1 ...
?$ Petal.Length: num ?1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 ...
?$ Petal.Width : num ?0.2 0.2 0.2 0.2 0.2 0.4 0.3 0.2 0.2 0.1 ...
?$ Species ? ? : Factor w/ 3 levels
"setosa","versicolor",..: 1 1 1 1 1 1 1 1 1 1 ...

> head(iris)
? Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1 ? ? ? ? ?5.1 ? ? ? ? 3.5 ? ? ? ? ?1.4 ? ? ? ? 0.2 ?setosa
2 ? ? ? ? ?4.9 ? ? ? ? 3.0 ? ? ? ? ?1.4 ? ? ? ? 0.2 ?setosa
3 ? ? ? ? ?4.7 ? ? ? ? 3.2 ? ? ? ? ?1.3 ? ? ? ? 0.2 ?setosa
4 ? ? ? ? ?4.6 ? ? ? ? 3.1 ? ? ? ? ?1.5 ? ? ? ? 0.2 ?setosa
5 ? ? ? ? ?5.0 ? ? ? ? 3.6 ? ? ? ? ?1.4 ? ? ? ? 0.2 ?setosa
6 ? ? ? ? ?5.4 ? ? ? ? 3.9 ? ? ? ? ?1.7 ? ? ? ? 0.4 ?setosa

And I would like to convert the last variable, Species, to numeric number.

For example, 'setosa'=1, and "versicolor"=2, other=3.

What code should I use? Here is my result from as.numeric(iris):

> as.numeric(iris)
Error: (list) object cannot be coerced to type 'double'