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

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Liviu Andronic

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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Rui Barradas

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

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)

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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Peter Ehlers

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

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
>>
>>
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Brian Diggs

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

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

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
>>>
>>>
>>
>> ______________________________________________
>> [hidden email] mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>

--
Brian S. Diggs, PhD
Senior Research Associate, Department of Surgery
Oregon Health & Science University

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Peter Ehlers

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

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
>>>>
>>>>
>>>
>>> ______________________________________________
>>> [hidden email] mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
>
>

Rui Barradas

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

Hello,

Em 10-07-2012 18:59, Peter Ehlers escreveu:

> 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
>

Good to know, was completely unaware of this indexing possibility.

Rui Barradas

>>
>> 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
>>>>>
>>>>>
>>>>
>>>> ______________________________________________
>>>> [hidden email] mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> PLEASE do read the posting guide
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>>
>>
>>
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Liviu Andronic

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

In reply to this post by Peter Ehlers

On Tue, Jul 10, 2012 at 4:53 PM, Peter Ehlers <[hidden email]> wrote:
> 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.
>
This one is an excellent solution, but yet another---what I
call---quirky behaviour from R.

Thanks all! Regards
Liviu

______________________________________________
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https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

David Winsemius

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

In reply to this post by Rui Barradas

On Jul 10, 2012, at 2:05 PM, Rui Barradas wrote:

> Hello,
>
> Em 10-07-2012 18:59, Peter Ehlers escreveu:
>> 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
>>

It would be difficult to be more compact than this:

> iris[1, ][NA,]
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
NA NA NA NA NA <NA>

--
David

>
> Good to know, was completely unaware of this indexing possibility.
>
> Rui Barradas
>
>>>
>>> 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
>>>>>>
>>>>>>
>>>>>
>>>>> ______________________________________________
>>>>> [hidden email] mailing list
>>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>>> PLEASE do read the posting guide
>>>>> http://www.R-project.org/posting-guide.html
>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>>
>>>>
>>>
>>>
>>
>> ______________________________________________
>> [hidden email] mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> [hidden email] mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT

______________________________________________
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https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Gabor Grothendieck

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

In reply to this post by Liviu Andronic

On Tue, Jul 10, 2012 at 9:15 AM, Liviu Andronic <[hidden email]> wrote:

Try this:

Try this:

> iris[NaN,]
Sepal.Length Sepal.Width Petal.Length Petal.Width Species
NA NA NA NA NA <NA>

--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com

______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

arun kirshna

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

In reply to this post by Liviu Andronic

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 <[hidden email]>
To: "[hidden email] Help" <[hidden email]>
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

--
Do you know how to read?
http://www.alienetworks.com/srtest.cfm
http://goodies.xfce.org/projects/applications/xfce4-dict#speed-reader
Do you know how to write?
http://garbl.home.comcast.net/~garbl/stylemanual/e.htm#e-mail

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

William Dunlap

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

Why does one want to replace a zero-row data.frame
with a one-row data.frame of NA's? Unless this is for
an external program that cannot handle zero-row inputs,
this suggests that there is an unnecessary limitation (i.e.,
a bug) in the R code that uses this data.frame.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf Of arun
> Sent: Wednesday, July 11, 2012 10:03 AM
> To: Liviu Andronic
> Cc: R help
> Subject: Re: [R] 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 <[hidden email]>
> To: "[hidden email] Help" <[hidden email]>
> 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
>
>
> --
> Do you know how to read?
> http://www.alienetworks.com/srtest.cfm
> http://goodies.xfce.org/projects/applications/xfce4-dict#speed-reader
> Do you know how to write?
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> and provide commented, minimal, self-contained, reproducible code.

Liviu Andronic

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

On Wed, Jul 11, 2012 at 9:56 PM, William Dunlap <[hidden email]> wrote:
> Why does one want to replace a zero-row data.frame
> with a one-row data.frame of NA's? Unless this is for
> an external program that cannot handle zero-row inputs,
> this suggests that there is an unnecessary limitation (i.e.,
> a bug) in the R code that uses this data.frame.
>
I'm running an apply(df, 1, f) function, where f() matches a df$string
in another matrix and fetches data associated with this string. When
no match is made I do not need a zero-row data frame, but to preserve
the structure of the original df I need a data frame with 1 row of
NAs. There may be a nicer approach, but I'm not aware of any.

Regards
Liviu

______________________________________________
[hidden email] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

William Dunlap

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

In that case, I think that using a subscript of NA is the
best way to go. It works for both matrices and data.frames
(unlike an integer larger than nrow(data)) and its meaning
is pretty clear.

Also, you will probably get better results if the function
in your call to apply() returns the index (perhaps NA) of a row
of a data.frame instead of the row itself. Then subscript that data.frame
once with the output of apply rather than subscripting it many
times and rbinding the results back together. This is natural
if you use match(), as it returns NA for no match (merge() does
this sort of thing).

Here is an example of this sort of thing when using a non-standard
sort of match. The following matches a long/lat pair to that of the
nearest city in the table, but returns NA if the point is too far from
any city:

nearestTo <- function (x, table, limit = 1)
{
stopifnot(all(is.element(c("long", "lat"), names(x))), all(is.element(c("long",
"lat"), names(table))))
dists <- sqrt((x["lat"] - table[, "lat"])^2 + (x["long"] -
table[, "long"])^2)
retval <- which.min(dists)
if (dists[retval] > limit) {
retval <- NA_integer_
}
retval
}

cities <- data.frame(
long = c(-117.833, -116.217, -123.083, -123.9, -121.733,
-117.033, -122.683, -122.333, -117.433),
lat = c(44.7833, 43.6, 44.05, 46.9833, 42.1667,
46.4, 45.5167, 47.6167, 47.6667),
row.names = c("Baker", "Boise", "Eugene", "Hoquiam",
"Klamath Falls", "Lewiston", "Portland",
"Seattle", "Spokane")
)

df <- data.frame(
long = c(-116.77, -123.68, -122.96, -120.81, -116.26,
-123.54, -121.22, -115.12),
lat = c(47.3, 44.53, 44.35, 45.99, 46.75, 43.78,
42.71, 46.66))

whichCity <- apply(df, 1, nearestTo, cities, limit=1)
whichCity
# [1] 9 3 3 NA 6 3 5 NA
cbind(df, nearbyCity = rownames(cities)[whichCity])
# long lat nearbyCity
# 1 -116.77 47.30 Spokane
# 2 -123.68 44.53 Eugene
# 3 -122.96 44.35 Eugene
# 4 -120.81 45.99 <NA>
# 5 -116.26 46.75 Lewiston
# 6 -123.54 43.78 Eugene
# 7 -121.22 42.71 Klamath Falls
# 8 -115.12 46.66 <NA>

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

> -----Original Message-----
> From: Liviu Andronic [mailto:[hidden email]]
> Sent: Wednesday, July 11, 2012 2:19 PM
> To: William Dunlap
> Cc: arun; R help
> Subject: Re: [R] fill 0-row data.frame with 1 line of NAs
>
> On Wed, Jul 11, 2012 at 9:56 PM, William Dunlap <[hidden email]> wrote:
> > Why does one want to replace a zero-row data.frame
> > with a one-row data.frame of NA's? Unless this is for
> > an external program that cannot handle zero-row inputs,
> > this suggests that there is an unnecessary limitation (i.e.,
> > a bug) in the R code that uses this data.frame.
> >
> I'm running an apply(df, 1, f) function, where f() matches a df$string
> in another matrix and fetches data associated with this string. When
> no match is made I do not need a zero-row data frame, but to preserve
> the structure of the original df I need a data frame with 1 row of
> NAs. There may be a nicer approach, but I'm not aware of any.
>
> Regards
> Liviu