On 2012-07-10 08:50, Brian Diggs wrote:
On 7/10/2012 7:53 AM, Peter Ehlers wrote:
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.
Using NA subscripting seems even better
Yes, you can subset with NA or any real number greater than 1.
Peter Ehlers
empty <- function(x) {
if(NROW(x) == 0) {
x[NA,]
} else {
x
}
}
It even preserves the factor nature of things:
> empty(iris[iris$Specis=='zz',])
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
NA NA NA NA NA <NA>
> str(empty(iris[iris$Specis=='zz',]))
'data.frame': 1 obs. of 5 variables:
$ Sepal.Length: num NA
$ Sepal.Width : num NA
$ Petal.Length: num NA
$ Petal.Width : num NA
$ Species : Factor w/ 3 levels "setosa","versicolor",..: NA
?
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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