Can't change the column names outputted by "gather" to be anything other than the default names

Question

I'm trying to use gather in the tidyr package, but I'm not able to change the outputted column names from the default names. For instance:

df = data.frame(time = 1:100,a = 1:100,b = 101:200)
df.long = df %>% gather("foo","bar",a:b)
colnames(df.long)

gives me

[1] "time"     "variable" "value"   

but shouldn't it be "time" "foo" "bar" ?

I can change "foo" and "bar" to anything I want, and it still gives me "variable" and "value" as my column names.

Help. What am I missing here?

Answer 1

This could possibly be a bug. If you are willing to try else, like melt() of data.table, you could do below:

# Need to load both data.table and reshape2
# For more information, could check ?data.table
library(reshape2); library(data.table)
setDT(df)
df %>% melt(id.vars = "time", variable.name = "foo", value.name = "bar")

> First 20 rows
    time foo bar
1:    1   a   1
2:    2   a   2
3:    3   a   3
4:    4   a   4
5:    5   a   5
6:    6   a   6
7:    7   a   7
8:    8   a   8
9:    9   a   9
10:   10   a  10
11:    1   b  11
12:    2   b  12
13:    3   b  13
14:    4   b  14
15:    5   b  15
16:    6   b  16
17:    7   b  17
18:    8   b  18
19:    9   b  19
20:   10   b  20