R: How to Delete All Columns in a Dataframe Except A Specified Few By String

Question

I have a data frame in R that consists of around 400 variables (as columns), though I only need 25 of them. While I know how to delete specific columns, because of the impracticality of deleting 375 variables - is there any method in which I could delete all of them, except the specified 25 by using the variable's string name?

Thanks.

`?subset`, e.g.: `subset(airquality, select = c(Ozone, Temp))` — zx8754, Apr 12 '16 at 07:06
You do not "delete 375 variables". You extract 25 columns. Read `help("[")`. — Roland, Apr 12 '16 at 07:06

score 6 · Answer 1 · answered Apr 12 '16 at 08:10

Sample example:

 df <- data.frame(a=1:5,b=6:10,c=11:15,d=16:20,e=21:25,f=26:30)  # Six columns
 df
    a  b  c  d  e  f
  1 1  6 11 16 21 26
  2 2  7 12 17 22 27
  3 3  8 13 18 23 28
  4 4  9 14 19 24 29
  5 5 10 15 20 25 30

 reqd <- as.vector(c("a","c","d","e")) # Storing the columns I want to extract as a vector
 reqd                                     
 [1] "a" "c" "d" "e"

 Result <- df[,reqd]       # Extracting only four columns
 Result
   a  c  d  e
 1 1 11 16 21
 2 2 12 17 22
 3 3 13 18 23
 4 4 14 19 24
 5 5 15 20 25

R: How to Delete All Columns in a Dataframe Except A Specified Few By String

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