To check data type of each column of data frame, you can use class function or str() function. You can use class() function with lapply() or sapply() function.

The following methods show how you can do it with syntax.

Method 1: Use class() With lapply() Function

lapply(df, class)

Method 2: Use class() With sapply() Function

sapply(df, class)

Method 3: Use str() Function

str(df)

The following examples show how to check data type of each column of data frame in R.

Using class() With lapply() Function

Let’s see how we can check data type of each column of data frame:

# Create data frame
df <- data.frame(Start_date=as.Date(c("2000-05-21","1998-03-28","2001-01-19","2003-04-27","2004-11-26","2008-11-25")),Machine_name = c("Machine1","Machine2","Machine3","Machine4","Machine5","Machine6"),Value = c(110,120,135,95,98,92),Working= c(TRUE,TRUE,FALSE,TRUE,FALSE,FALSE))

# Check datatype
lapply(df,class)

Output:

$Start_date
[1] "Date"

$Machine_name
[1] "character"

$Value
[1] "numeric"

$Working
[1] "logical"

The output shows data type of each column of data frame.

Using class() With sapply() Function

Let’s use class() function with sapply() to check data type in R:

# Create data frame
df <- data.frame(Start_date=as.Date(c("2000-05-21","1998-03-28","2001-01-19","2003-04-27","2004-11-26","2008-11-25")),Machine_name = c("Machine1","Machine2","Machine3","Machine4","Machine5","Machine6"),Value = c(110,120,135,95,98,92),Working= c(TRUE,TRUE,FALSE,TRUE,FALSE,FALSE))

# Check datatype
sapply(df,class)

  Start_date Machine_name        Value      Working 
      "Date"  "character"    "numeric"    "logical"

Here the output shows data type of each column of data frame

Use str() Function

Let’s see how we can use str() function in R:

# Create data frame
df <- data.frame(Start_date=as.Date(c("2000-05-21","1998-03-28","2001-01-19","2003-04-27","2004-11-26","2008-11-25")),Machine_name = c("Machine1","Machine2","Machine3","Machine4","Machine5","Machine6"),Value = c(110,120,135,95,98,92),Working= c(TRUE,TRUE,FALSE,TRUE,FALSE,FALSE))

# Check data type
str(df)

Output:

'data.frame':	6 obs. of  4 variables:
 $ Start_date  : Date, format: "2000-05-21" "1998-03-28" "2001-01-19" ...
 $ Machine_name: chr  "Machine1" "Machine2" "Machine3" "Machine4" ...
 $ Value       : num  110 120 135 95 98 92
 $ Working     : logi  TRUE TRUE FALSE TRUE FALSE FALSE

Here output shows not only datatype of each column but also it shows number of rows and columns.