Create empty data frame with column names by assigning a string vector? [duplicate]

Question

Create an empty data frame:

y <- data.frame()

Assign x, a string vector, to y as its column names:

    x <- c("name", "age", "gender")
    colnames(y) <- x

Result:

Error in colnames<-(*tmp*, value = c("name", "age", "gender")) : 'names' attribute [3] must be the same length as the vector [0]

Actually, the x length is dynamic, so

y <- data.frame(name=character(), age=numeric(), gender=logical())

is not an efficient way to name the column. How can I solve the problem?

If you want to create an empty data.frame with dynamic names (colnames in a variable), this can help: names <- c("v","u","w") df <- data.frame() for (k in names) df[[k]]<-as.numeric() You can change the type as well if you need so. — Ali Khosro
– Ali Khosro, Commented Mar 3, 2017 at 20:11

MohammadHosseinZiyaaddini · Accepted Answer · 2021-01-01 02:01:47Z

414

How about:

df <- data.frame(matrix(ncol = 3, nrow = 0))
x <- c("name", "age", "gender")
colnames(df) <- x

To do all these operations in one-liner:

setNames(data.frame(matrix(ncol = 3, nrow = 0)), c("name", "age", "gender"))

#[1] name   age    gender
#<0 rows> (or 0-length row.names)

Or

data.frame(matrix(ncol=3,nrow=0, dimnames=list(NULL, c("name", "age", "gender"))))

edited Jan 1, 2021 at 2:01

MohammadHosseinZiyaaddini

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answered Sep 22, 2015 at 8:53

Ronak Shah

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6 Comments

DD chen Over a year ago

hello, do you have an easy way to add columns (type = character) which colnames are ``` new_col_names <- c("new1", "new2") ``` ? I tried this : ``` df[, new_col_names ] <- NULL ``` , this doesn't work

Ronak Shah Over a year ago

@DDchen If you have a dataframe df, this should work df[new_col_names] <- NA_character_

Julien Over a year ago

setNames(data.frame(matrix(ncol = length(col), nrow = 0)), col <- c("name", "age", "gender")) for a more dynamic way of doing it

mpag Over a year ago

@Julien Isn't assigning a variable within the context of another function call considered bad practice in R? Do we know that the second argument is always evaluated before the first is called?

Julien Over a year ago

Good question, it's indeed risky. But it does work here

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