[SOLVED] Specifying column names in a data.frame changes spaces to "."

Specifying column names in a data.frame changes spaces to "."

Let's say I have a data.frame, like so:

x <- c(1:10,1:10,1:10,1:10,1:10,1:10,1:10,1:10,1:10,1:10)
df <- data.frame("Label 1"=x,"Label 2"=rnorm(100))

head(df,3)

returns:

  Label.1    Label.2
1       1  1.9825458
2       2 -0.4515584
3       3  0.6397516

How do I get R to stop automagically replacing the space with a period in the column name? ie, "Label 1" instead of "Label.1".

Solution

You don't.

With the space you desire the format would not satisfy the requirements for an identifier that come to play when you use df$column.1 -- that could not cope with a space. So see the make.names() function for details or an example:

> make.names(c("Foo Bar", "tic tac"))
[1] "Foo.Bar" "tic.tac"  
>

Edit eleven years later: The answer still stands that R prefers column names can be valid variable names. But R is flexible: if you insist you can use the other form _but then need to require the not-otherwise-valid-within-the-language column names explicitly:

> x <- c(1:10,1:10,1:10,1:10,1:10,1:10,1:10,1:10,1:10,1:10)
> df <- data.frame("Label 1"=x,"Label 2"=rnorm(100), check.names=FALSE)
> summary( df$`Label 2` )
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
-2.2719 -0.7148 -0.0971 -0.0275  0.6559  2.5820 
>

So by saying check.names=FALSE we override the default (and sensible) check, and by wrapping the identifier in backticks we can access the column.