Is there a way to reference specific code

Question

I have a sample dataframe below df.

    df
     ColA       ColB      ColC
      A           B         2
      D           B         3
      D           A         4

To get values in ColA, we can use df$ColA. But can we not reference here. For example

    sa <- names(Filter(is.factor,df))
    sa 
    sa
   [1] "ColA" "ColB"

If I use the below code, I am not getting elements of ColA. Should be getting right? Or is there way to do this

     df$sa[1]

Error in .subset2(x, i, exact = exact) : subscript out of bounds . Getting this error — Dev P, Sep 29 '19 at 05:18
Just noticed `length(sa) > 1L`. see https://stackoverflow.com/questions/1169456/the-difference-between-bracket-and-double-bracket-for-accessing-the-el — MichaelChirico, Sep 29 '19 at 09:12

score 0 · Answer 1 · answered Sep 29 '19 at 05:10

0

We can't reference columns with $ when having sa as character vector. We can do

df[sa[1]]

#  ColA
#1    A
#2    D
#3    D

Or with dplyr

library(dplyr)
df %>% select(sa[1])

answered Sep 29 '19 at 05:10

Ronak Shah

1 Answers1