R: How to Delete All Columns in a Dataframe Except A Specified Few By String : <p>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? </p>

<p>Thanks.  </p>
