How to find the class of columns of an R data frame?

To find the class of columns of an R data frame, we can use class function along with sapply and as.data.frame function.

For Example, if we have a data frame called DF then we can find the class of columns in DF by using the command as follows −

data.frame(sapply(DF,class))

Example 1

Consider the below data frame −

head(mtcars,20) 

The following dataframe is created

                      mpg  cyl   disp   hp  drat     wt   qsec  vs am gear carb Mazda RX4           21.0    6  160.0  110  3.90  2.620  16.46   0  1    4    4 Mazda RX4 Wag       21.0    6  160.0  110  3.90  2.875  17.02   0  1    4    4 Datsun 710          22.8    4  108.0   93 3.85  2.320  18.61   1  1    4    1 Hornet 4 Drive      21.4    6  258.0  110  3.08  3.215  19.44   1  0    3    1 Hornet Sportabout   18.7    8  360.0  175  3.15 3.440 17.02 0 0 3 2 Valiant             18.1 6 225.0 105 2.76 3.460 20.22 1 0 3 1 Duster 360          14.3 8 360.0 245 3.21 3.570 15.84 0 0 3 4 Merc 240D           24.4 4 146.7 62 3.69 3.190 20.00 1 0 4 2 Merc 230            22.8 4 140.8 95 3.92 3.150 22.90 1 0 4 2 Merc 280            19.2 6 167.6 123 3.92 3.440 18.30 1 0 4 4 Merc 280C           17.8 6 167.6 123 3.92 3.440 18.90 1 0 4 4 Merc 450SE          16.4 8 275.8 180 3.07 4.070 17.40 0 0 3 3 Merc 450SL          17.3 8 275.8 180 3.07 3.730 17.60 0 0 3 3 Merc 450SLC         15.2 8 275.8 180 3.07 3.780 18.00 0 0 3 3 Cadillac Fleetwood  10.4 8 472.0 205 2.93 5.250 17.98 0 0 3 4 Lincoln Continental 10.4 8 460.0 215 3.00 5.424 17.82 0 0 3 4 Chrysler Imperial   14.7 8 440.0 230 3.23 5.345 17.42 0 0 3 4 Fiat 128            32.4 4 78.7 66 4.08 2.200 19.47 1 1 4 1 Honda Civic         30.4 4 75.7 52 4.93 1.615 18.52 1 1 4 2 Toyota Corolla      33.9 4 71.1 65 4.22 1.835 19.90 1 1 4 1

To check the class of columns in mtcars on the above created data frame, add the following code to the above snippet −

as.data.frame(sapply(mtcars,class)) 

Output

If you execute all the above given snippets as a single program, it generates the following Output −

     sapply(mtcars, class) mpg              numeric cyl              numeric disp             numeric hp               numeric drat             numeric wt               numeric qsec             numeric vs               numeric am               numeric gear             numeric carb             numeric

Example 2

Consider the following data frame −

head(CO2,20) 

If you execute the above given snippet, it generates the following Output −

  Plant    Type   Treatment   conc   uptake 1   Qn1  Quebec  nonchilled     95     16.0 2   Qn1  Quebec  nonchilled    175     30.4 3   Qn1  Quebec  nonchilled    250     34.8 4   Qn1  Quebec  nonchilled 350 37.2 5   Qn1  Quebec  nonchilled 500 35.3 6   Qn1  Quebec  nonchilled 675 39.2 7   Qn1  Quebec  nonchilled 1000 39.7 8   Qn2  Quebec  nonchilled 95 13.6 9   Qn2  Quebec  nonchilled 175 27.3 10  Qn2  Quebec  nonchilled 250 37.1 11  Qn2  Quebec  nonchilled 350 41.8 12  Qn2  Quebec  nonchilled 500 40.6 13  Qn2  Quebec  nonchilled 675 41.4 14  Qn2  Quebec  nonchilled 1000 44.3 15  Qn3  Quebec  nonchilled 95 16.2 16  Qn3  Quebec  nonchilled 175 32.4 17  Qn3  Quebec  nonchilled 250 40.3 18  Qn3  Quebec  nonchilled 350 42.1 19  Qn3  Quebec  nonchilled 500 42.9 20  Qn3 Quebec nonchilled 675 43.9

To check the class of columns in CO2 on the above created data frame, add the following code to the above snippet −

as.data.frame(sapply(CO2,class)) 

Output

If you execute all the above given snippets as a single program, it generates the following Output −

 Plant Type Treatment conc uptake 1 ordered factor factor numeric numeric 2 factor factor factor numeric numeric

Example 3

Consider the following data frame −

head(sleep,20) 

Output

If you execute the above given snippet, it generates the following Output −

   extra group ID 1    0.7     1  1 2   -1.6     1  2 3   -0.2     1  3 4   -1.2     1  4 5   -0.1     1  5 6    3.4     1  6 7    3.7     1  7 8    0.8     1  8 9    0.0     1  9 10   2.0     1 10 11   1.9     2  1 12   0.8     2  2 13   1.1     2  3 14   0.1     2  4 15  -0.1     2  5 16   4.4     2  6 17   5.5     2  7 18   1.6     2  8 19   4.6     2 9 20 3.4 2 10

To check the class of columns in sleep on the above created data frame, add the following code to the above snippet −

as.data.frame(sapply(sleep,class)) 

Output

If you execute all the above given snippets as a single program, it generates the following Output −

 sapply(sleep, class) extra numeric group factor ID factor