How to create a new column in an empty dataframe in R [duplicate]

Question

Here is my code :

dfNbMatchSurface = data.frame()
print(dfNbMatchSurface)
dfNbMatchSurface$test <- "exp"
write.csv(dfNbMatchSurface, file = "NbMatchSurface.csv")

And i want to create an empty dataframe with a new test column that is empty and call "exp"

How to do that ?

I've also tried this :

dfNbMatchSurface = data.frame()
print(dfNbMatchSurface)
dfNbMatchSurface$test <- NA 
write.csv(dfNbMatchSurface, file = "NbMatchSurface.csv")

I have thos error :

Error in `$<-.data.frame`(`*tmp*`, test, value = "exp") : 
  replacement has 1 row, data has 0

Regards and thanks

You might do this df <- data.frame(test = NA). Please tell us your intended purpose of initializing an empty data.frame, maybe we can give better advice then. — Manuel Bickel
– Manuel Bickel, Commented Nov 27, 2017 at 9:43

LAP · Accepted Answer · 2017-11-27 09:44:53Z

5

You can use character() to assign a class to the variable without including values (other classes also work, like factor(), integer() or numeric()).

df <- data.frame()
> df
data frame with 0 columns and 0 rows

df$var1 <- character()
> df
[1] var1
<0 rows> (or row.names with length 0)

answered Nov 27, 2017 at 9:44

LAP

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