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

Hi,

Try this:
 .xa<-iris[1,][rep(NA,length(iris),1),]
.xa
#?? Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#NA?????????? NA????????? NA?????????? NA????????? NA??? <NA>
#or

.xb<-iris[1,][rep(NA,ncol(iris),1),]
?.xb
#?? Sepal.Length Sepal.Width Petal.Length Petal.Width Species
#NA?????????? NA????????? NA?????????? NA????????? NA??? <NA>


A.K.


----- Original Message -----
From: Liviu Andronic <landronimirc at gmail.com>
To: "r-help at r-project.org Help" <r-help at r-project.org>
Cc: 
Sent: Tuesday, July 10, 2012 9:15 AM
Subject: [R] fill 0-row data.frame with 1 line of NAs

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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