How do I get the classes of all columns in a data frame?

Question

What is an easy way to find out what class each column is in a data frame is?

Answer 1

To get the classes of all the columns in a data frame, you can use the following methods:

Using lapply():

lapply(iris, class)

$Sepal.Length

[1] "numeric"

$Sepal.Width

[1] "numeric"

$Petal.Length

[1] "numeric"

$Petal.Width

[1] "numeric"

$Species

[1] "factor"

Using str() function:

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 ...

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