A daily R language tip (4) - get the data type (single variable, each column in the dataframe data frame, each element)

Knowledge point self-test

1. What are the object types in R? What are the data types?
2. How to get the data type of a variable?
3. How can I get the data type of each column in df like below?

> df=data.frame(1:5,c(T,F,T,F,F),letters[2:6])
> df
  X1.5 c.T..F..T..F..F. letters.2.6.
1    1             TRUE            b
2    2            FALSE            c
3    3             TRUE            d
4    4            FALSE            e
5    5            FALSE            f

Answer

1. There are seven object types in R

• vector vector
• list list
• matrix matrix
• array array
• factor factor
• data.frame data frame
• scalar scalar

There are many types of data, we usually come into contact with the following types

• numeric
• complex
• logical
• character
• null
• double
• list
• …

First understand whether you want an object type or a data type!!!

get data type

• typeof()
• mode()
• storage.mode()

> typeof(df)
[1] "list"
> mode(df)
[1] "list"
> storage.mode(df)
[1] "list"

3. Use the str() function to easily get the structure of an R object

> str(df)
'data.frame':	5 obs. of  3 variables:
 $ X1.5            : int  1 2 3 4 5
 $ c.T..F..T..F..F.: logi  TRUE FALSE TRUE FALSE FALSE
 $ letters.2.6.    : Factor w/ 5 levels "b","c","d","e",..: 1 2 3 4 5

There is also a function that can also see the detailed information of the R object, but it can only see the object type, and does not display the data type of the specific column

> attributes(df)
$names
[1] "X1.5"             "c.T..F..T..F..F." "letters.2.6."    

$class
[1] "data.frame"

$row.names
[1] 1 2 3 4 5