Adding a new column next to each existing column that matches a certain column name pattern in R / tidyverse

Question

In a dataframe I want to add a new column next each column whose name matches a certain pattern, for example whose name starts with "ip_" and is followed by a number. The name of the new columns should follow the pattern "newCol_" suffixed by that number again. The values of the new columns should be NA's.

So this dataframe:

should be transformed to that dataframe:

A tidiverse solution with use of regex is much appreciated!

Sample data:

df <- data.frame( ID = c("1", "2"), ip_1 = c(2,3), ip_9 = c(5,7), ip_39 = c(11,13), in_1 = c("B", "D"), in_2 = c("A", "H"), in_3 = c("D", "A") )

Ronak Shah · Accepted Answer · 2022-02-12 02:49:41Z

To get the columns is easy with across -

library(dplyr) df %>% mutate(across(starts_with('ip'), ~NA, .names = '{sub("ip", "newCol", .col)}')) # ID ip_1 ip_9 ip_39 in_1 in_2 in_3 newCol_1 newCol_9 newCol_39 #1 1 2 5 11 B A D NA NA NA #2 2 3 7 13 D H A NA NA NA

To get the columns in required order -

library(dplyr) df %>% mutate(across(starts_with('ip'), ~NA, .names = '{sub("ip", "newCol", .col)}')) %>% select(ID, starts_with('in'), order(suppressWarnings(readr::parse_number(names(.))))) %>% select(ID, ip_1:newCol_39, everything()) # ID ip_1 newCol_1 ip_9 newCol_9 ip_39 newCol_39 in_1 in_2 in_3 #1 1 2 NA 5 NA 11 NA B A D #2 2 3 NA 7 NA 13 NA D H A

Salix · Accepted Answer · 2022-02-22 00:31:55Z

To add the new NA columns :

df[, sub("^ip", "newCol", grep("^ip", names(df), value = TRUE))] <- NA

To reorder them :

df <- df[, order(c(grep("newCol", names(df), invert = TRUE), grep("^ip", names(df))))]

edit :

If it's something you (or whoever stumble here) plan on doing often, you can use this function :

insertCol <- function(x, ind, col.names = ncol(df) + seq_along(colIndex), data = NA){ out <- x out[, col.names] <- data out[, order(c(col(x)[1,], ind))] }

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