Add Named Columns to Data Frame in R [duplicate] - r

Question

This question already has answers here:
How to add multiple columns to a data.frame in one go?
(2 answers)
Closed 4 years ago.
I am in the process of reformatting a few data frames and was wondering if there is a more efficient way to add named columns to data frames, rather than the below:
colnames(df) <- c("c1", "c2)
to rename the current columns and:
df$c3 <- ""
to create a new column.
Is there a way to do this in a quicker manner? I'm trying to add dozens of named columns and this seems like an inefficient way of going through the process.

Answer 1

use your method in a shorter way:
cols_2_add=c("a","b","c","f")
df[,cols_2_add]=""

Answer 2

A way to add additional columns can be achieved using merge. Apply merge on existing dataframe with the one created with a desired columns and empty rows. This will be helpful if you want to create columns of different types.
For example:
# Existing dataframe
df <- data.frame(x=1:3, y=4:6)
#use merge to create say desired columns as a, b, c, d and e
merge(df, data.frame(a="", b="", c="", d="", e=""))
# Result
# x y a b c d e
#1 1 4
#2 2 5
#3 3 6
# Desired columns of different types
library(dplyr)
bind_rows(df, data.frame(a=character(), b=numeric(), c=double(), d=integer(),
e=as.Date(character()), stringsAsFactors = FALSE))
# x y a b c d e
#1 1 4 <NA> NA NA NA <NA>
#2 2 5 <NA> NA NA NA <NA>
#3 3 6 <NA> NA NA NA <NA>

Answer 3

A simple loop can help here
name_list <- c('a1','b1','c1','d1')
# example df
df <- data.frame(a = runif(3))
# this adds a new column
for(i in name_list)
{
df[[i]] <- runif(3)
}
# output
a a1 b1 c1 d1
1 0.09227574 0.08225444 0.4889347 0.2232167 0.8718206
2 0.94361151 0.58554887 0.7095412 0.2886408 0.9803941
3 0.22934864 0.73160433 0.6781607 0.7598064 0.4663031
# in case of data.table, for-set provides faster version:
# example df
df <- data.table(a = runif(3))
for(i in name_list)
set(df, j=i, value = runif(3))