Why data frame column names different using = and <

This question already has an answer here:

What are the differences between “=” and “<-” in R? 6 answers

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The <- operator not only assigns objects but creates them in the parent environment unlike = operator

Renaming columns slightly:

df1 <- data.frame(a1 = 1:5, b1 = 11:15)



df1
#   a1  b1
# 1 1 11
# 2 2 12
# 3 3 13
# 4 4 14
# 5 5 15


#The objects are only created in the dataframee but not in environment  
# > exists(x = "a1")
#[1] FALSE
#> exists(x = "b1")
#[1] FALSE


#The objects are not only in created in the dataframe as well as in the environment

df2 <- data.frame(a2 <- 1:5, b2 <- 11:15)
df2
#   a2....1.5 b2....11.15
# 1        1         11
# 2        2         12
# 3        3         13
# 4        4         14
# 5        5         15

# > exists(x = "a2")
#[1] TRUE
#> exists(x = "b2")
#[1] TRUE

---

If you want to have the column names as a, b, the correct syntax should be

data.frame(a=1:5, b=1:5)

The statement

data.frame(a <- 1:5, b <- 1:5)

R interprets it as if no column names are provided, so it treats the entire expression 'a <- 1:5' as the first column name, but there are 2 spaces and 3 illegal characters '<', '-', ':' that are not allowed in a column name, so each of them is changed to the character '.', hence you get the entire 'a....1.5' as the first column name, same goes for the second column.

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