# How to convert a factor variable to a numeric variable

Converting factors to numeric or character values and vice-versa is used in a variety of cases.

### Factor to String

```> 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 ...
```

Let’s convert the Species column from factor to string

```> iris_1 = iris
> iris_1\$Species = as.character(iris\$Species)
> str(iris_1)
'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     : chr  "setosa" "setosa" "setosa" "setosa" ...
```

### String to Factor

Let’s revert to the original factor based iris dataset.

```> iris_2 = iris_1
> iris_2\$Species = as.factor(iris\$Species)
> str(iris_2)
'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 ...
```

### Factor to Numeric

```> iris_3 = iris
> iris_3\$Species = as.numeric(iris\$Species)
> iris_3
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
1            5.1         3.5          1.4         0.2       1
2            4.9         3.0          1.4         0.2       1
3            4.7         3.2          1.3         0.2       1
4            4.6         3.1          1.5         0.2       1
```

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