How do I delete columns in a dataframe if the name begins with X?

Question

How can I delete all columns in an R dataframe whose names begin with X?

Here is how I want it to look (before and after):

Before:

¦ 1COL1 ¦ 2COL ¦ 3COL ¦ XCOL ¦ 4COL ¦ XXCOL ¦

After:

¦ 1COL1 ¦ 2COL ¦ 3COL ¦ 4COL ¦

Answer 1

You can delete the column whose name begin with X using grep and with its invert property set as TRUE. With invert = TRUE it returns the indices which don't match the given pattern.

df_1 <- df[grep("^X", colnames(df), invert = TRUE)]

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This can also be done with grepl which returns logical vector.

df[!grepl("^X", colnames(df))]