[R] Removing variables from data frame with a wile card

[Steven Yen]

Great, Thanks. Now I have many options.

Steven from iPhone

> On Feb 13, 2023, at 10:52 AM, Andrew Simmons <akwsimmo using gmail.com> wrote:
> 
> What I meant is that that
> 
> mydata[, !grepl("^yr", colnames(mydata)), drop = FALSE]
> 
> and
> 
> mydata[!grepl("^yr", colnames(mydata))]
> 
> should be identical. Some people would prefer the first because the
> indexing looks the same as matrix indexing, whereas some people would
> prefer the second because it is more efficient. However, I would argue
> it is exactly as efficient. You can see from the first few lines of
> `[.data.frame` when the first index is missing and the second is
> provided, it does almost the same thing as if only the first index
> provided.
> 
>> On Sun, Feb 12, 2023 at 9:38 PM Steven Yen <styen using ntu.edu.tw> wrote:
>> 
>> x[“V2”] would retain columns of x headed by V2. What I need is the opposite——I need a data grime with those columns excluded.
>> 
>> Steven from iPhone
>> 
>> On Feb 13, 2023, at 9:33 AM, Rolf Turner <r.turner using auckland.ac.nz> wrote:
>> 
>> 
>> On Sun, 12 Feb 2023 14:57:36 -0800
>> Jeff Newmiller <jdnewmil using dcn.davis.ca.us> wrote:
>> 
>> x["V2"]
>> 
>> 
>> is more efficient than using drop=FALSE, and perfectly normal syntax
>> 
>> (data frames are lists of columns).
>> 
>> 
>> <SNIP>
>> 

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