How to drop all variables that do not cointain a string or another in R

Question

I manage to select all variables that contains an specific string in its name by:

df[grep("string1|string2",names(df))]

But what I really want to do is to keep those variables and drop the rest. I can do:

df2<-df[grep("string1|string2",names(df))]

But was wondering if I could simply drop those variables I am not interested in instead of creating another data frame. I tried:

null<-X_total[grep("!(mean|std)",names(X_total))

But did not work.

Welcome to SO! Try `grepl`, which returns a logical vector, which you can easily negate: `!grepl("(mean|std)", names(X_total)`. — tonytonov, Sep 26 '15 at 18:01
Have a look at [How to drop columns by name in a dataframe](https://stackoverflow.com/questions/5234117/how-to-drop-columns-by-name-in-a-data-frame?rq=1) — LinkBerest, Sep 26 '15 at 18:01

score 1 · Accepted Answer · answered Sep 26 '15 at 18:14

Using dplyr, dropping all variables containing the strings Species or Sepal:

library(dplyr)
df <- select(iris, -matches("Species|Sepal"))

Output:

head(df, 3)
 Petal.Length Petal.Width
1          1.4         0.2
2          1.4         0.2
3          1.3         0.2

1 Answers1