Creating sequence of columns in R

Question

How can I create a sequence of columns (let's say X1, X2, ..., X100) with their value dependent on column index (1-100) with or (ideally) without using a for loop?

Below is my attempt with for loop (it's not working - I think it has something to do with the usage of paste to create the names of columns. But I believe it describes well I would like to achieve.

data <- runif(10)
data <- as_tibble(data)
for (i in 1:100){
  data <- data %>% mutate(paste('X', i, sep = '') = (value > 0.01 * i))
}

akrun · Accepted Answer · 2018-03-19 06:57:49Z

3

We can use map with !!

library(tidyverse)
map(1:100, ~ data %>% 
              transmute(!! paste0("X", .x) := value > 0.01 * .x)) %>% 
   bind_cols(data, .)

Or with for loop

for (i in 1:100){
     data <- data %>% 
                  mutate(!! paste('X', i, sep = '') := (value > 0.01 * i))
 }

edited Mar 19, 2018 at 6:57

answered Mar 19, 2018 at 6:48

akrun

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2 Comments

jakes Over a year ago

That's a cool expression! Could you explain the use of double exclamation mark as I can't find what's its meaning?

akrun Over a year ago

@jakes The assignment operator is := is used in data.table, but it is introduced recently in dplyr

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