[R] fill 0-row data.frame with 1 line of NAs

[Peter Ehlers]

On 2012-07-10 06:57, Rui Barradas wrote:
> Hello,
>
> If you write a function, it becomes less convoluted...
>
>
> empty <- function(x){
> 	if(NROW(x) == 0){
> 		y <- rep(NA, NCOL(x))
> 		names(y) <- names(x)
> 		y
> 	}else x
> }
>
> (.xb <- iris[ iris$Species=='zz', ])
> empty(.xb)

Both this and Liviu's original solution destroy the
factor nature of 'Species' (which may not matter, of
course). How about

   (.xb <- iris[ iris$Species=='zz', ])
   .xb <- .xb[1, ]   # this probably shouldn't work, but it does.

?

Peter Ehlers

>
>
> Hope this helps,
>
> Rui Barradas
>
> Em 10-07-2012 14:15, Liviu Andronic escreveu:
>> Dear all
>> Is there a simpler method to achieve the following: When I obtain an
>> empty data.frame after subsetting, I need for it to contain one line
>> of NAs. Here's a dummy example:
>>> (.xb <- iris[ iris$Species=='zz', ])
>> [1] Sepal.Length Sepal.Width  Petal.Length Petal.Width  Species
>> <0 rows> (or 0-length row.names)
>>> dim(.xb)
>> [1] 0 5
>>> (.xa <- data.frame(matrix(rep(NA, ncol(.xb)), 1)))
>>     X1 X2 X3 X4 X5
>> 1 NA NA NA NA NA
>>> names(.xa) <- names(.xb)
>>> (.xb <- .xa)
>>     Sepal.Length Sepal.Width Petal.Length Petal.Width Species
>> 1           NA          NA           NA          NA      NA
>>
>>
>> The solution I came up with is way too convoluted. Anything simpler? Regards
>> Liviu
>>
>>
>
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