How to extract only factor columns name from an R data frame?

To extract only factor column names from an R data frame, we can use names function with Filter by selecting only factor columns using as.factor. For example, if we have a data frame called df that contains some factor columns then the extraction of names of these factor columns can be done by using names(Filter(is.factor,df)).

Consider the below data frame −

Example

 Live Demo

x1<-factor(sample(c("Male","Female"),20,replace=TRUE)) x2<-rpois(20,5) df1<-data.frame(x1,x2) df1

Output

    x1    x2 1 Female  4 2   Male  7 3   Male  9 4 Female  3 5   Male  10 6 Female  4 7 Female  2 8 Female  1 9 Female  6 10 Female 7 11 Female 5 12   Male 5 13   Male 6 14 Female 4 15   Male 7 16   Male 3 17   Male 2 18   Male 4 19   Male 9 20 Female 6

Extracting names of factor column df1 −

names(Filter(is.factor,df1))

[1] "x1"

Example

 Live Demo

y1<-rnorm(20) y2<-rnorm(20,524,32.14) y3<-factor(sample(c("Hot","Cold"),20,replace=TRUE)) df2<-data.frame(y1,y2,y3) df2

Output

      y1            y2        y3 1   1.14683171   494.4162    Hot 2   0.91868842   580.5509    Hot 3   -0.17573235  534.0396    Cold 4   -0.02975191  488.0148    Cold 5   -0.26811263  492.4373    Hot 6   0.66937789   458.3491    Hot 7   0.47413241   488.5430   Cold 8  0.28988748   495.5700     Hot 9  -0.29068059   509.0902   Cold 10  -0.88108903  484.8437   Hot 11  -0.33612356  535.9354   Hot 12  0.40103781   510.7365   Hot 13  -0.92194471  521.3352   Hot 14  1.25918659   520.2907   Hot 15  -1.22533456  443.9293   Cold 16  1.81055353   494.4451   Hot 17  0.43367087   530.8559   Cold 18  1.63945140   489.3504   Cold 19  -1.55321040   541.3161  Cold 20  -1.02131445   510.2723   Cold

Extracting names of factor column df2 −

names(Filter(is.factor,df2))

[1] "y3"