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Robin Hankin

2003-Feb-13 23:38 UTC

[R] generic handling of NA and NaN and NULL

Hello everybody


I have a generic problem which the following toy function illustrates:

f <- function(n) {
  if(abs(n) < pi) {
    return(TRUE)
  } else {
    return(FALSE)
  }
}
                   
I want it to return TRUE if abs(n)<pi and FALSE otherwise.  f() is
fine as far as it goes, but does not deal well with NA or NaN or NULL
(I want these to signal some problem with the argument (ie return
FALSE), but not to stop execution of f().  In particular, I want f()
to pass R CMD check )-:

R> f(NA)
Error in if (abs(n) < pi) { : missing value where logical needed

R> f(NULL)
Error in abs(n) : non-numeric argument to function


So, how best to patch f() up?  The best I could come up with was:

f2 <- function(n) {
  if(is.null(n)){return(FALSE)}
  if(is.na(n)){return(FALSE)}
  if(abs(n) < pi) {
    return(TRUE)
  } else {
    return(FALSE)
  }
}

This can't be the best way!  Anyway, f2() isn't right: f2(numeric(0))
fails; note that

R> if(is.na(numeric(0))){print("asdf")}

falls over.  help.search("trap") was not very helpful.  try()
doesn't
help either:

R> try(if(1==NA){print("asdf")})
Error in if (1 == NA) { : missing value where logical needed



QUESTION: how to make f() not give an error under any circumstances?






-- 

Robin Hankin, Lecturer,
School of Geography and Environmental Science
Tamaki Campus
Private Bag 92019 Auckland
New Zealand

r.hankin at auckland.ac.nz
tel 0064-9-373-7599 x6820; FAX 0064-9-373-7042

Spencer Graves

2003-Feb-14 00:21 UTC

head link

[R] generic handling of NA and NaN and NULL

How about:

 > f3 <- function(n){
+   n.pi <- (abs(n)<pi)
+   n.pi[is.na(n.pi)] <- F
+   n.pi
+ }
 >
 > f3(c(1, 5, NA))
[1]  TRUE FALSE FALSE
 >

Spencer Graves

Robin Hankin wrote:> Hello everybody
> 
> 
> I have a generic problem which the following toy function illustrates:
> 
> f <- function(n) {
>   if(abs(n) < pi) {
>     return(TRUE)
>   } else {
>     return(FALSE)
>   }
> }
>                    
> I want it to return TRUE if abs(n)<pi and FALSE otherwise.  f() is
> fine as far as it goes, but does not deal well with NA or NaN or NULL
> (I want these to signal some problem with the argument (ie return
> FALSE), but not to stop execution of f().  In particular, I want f()
> to pass R CMD check )-:
> 
> R> f(NA)
> Error in if (abs(n) < pi) { : missing value where logical needed
> 
> R> f(NULL)
> Error in abs(n) : non-numeric argument to function
> 
> 
> So, how best to patch f() up?  The best I could come up with was:
> 
> f2 <- function(n) {
>   if(is.null(n)){return(FALSE)}
>   if(is.na(n)){return(FALSE)}
>   if(abs(n) < pi) {
>     return(TRUE)
>   } else {
>     return(FALSE)
>   }
> }
> 
> This can't be the best way!  Anyway, f2() isn't right:
f2(numeric(0))
> fails; note that
> 
> R> if(is.na(numeric(0))){print("asdf")}
> 
> falls over.  help.search("trap") was not very helpful.  try()
doesn't
> help either:
> 
> R> try(if(1==NA){print("asdf")})
> Error in if (1 == NA) { : missing value where logical needed
> 
> 
> 
> QUESTION: how to make f() not give an error under any circumstances?
> 
> 
> 
> 
> 
>

Liaw, Andy

2003-Feb-14 00:26 UTC

head link

[R] generic handling of NA and NaN and NULL

Try:

f <- function(n) {
  if(is.null(n) || is.na(n) || abs(n) < pi) {
    return(FALSE)
  } else {
    return(TRUE)
  }
}

Note that the order of the conditions inside if() matters: is.na(n) only
gets evaluated if is.null(n) is FALSE, and so on.

Andy
> -----Original Message-----
> From: Robin Hankin [mailto:r.hankin at auckland.ac.nz]
> Sent: Thursday, February 13, 2003 5:36 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] generic handling of NA and NaN and NULL
> 
> 
> Hello everybody
> 
> 
> I have a generic problem which the following toy function illustrates:
> 
> f <- function(n) {
>   if(abs(n) < pi) {
>     return(TRUE)
>   } else {
>     return(FALSE)
>   }
> }
>                    
> I want it to return TRUE if abs(n)<pi and FALSE otherwise.  f() is
> fine as far as it goes, but does not deal well with NA or NaN or NULL
> (I want these to signal some problem with the argument (ie return
> FALSE), but not to stop execution of f().  In particular, I want f()
> to pass R CMD check )-:
> 
> R> f(NA)
> Error in if (abs(n) < pi) { : missing value where logical needed
> 
> R> f(NULL)
> Error in abs(n) : non-numeric argument to function
> 
> 
> So, how best to patch f() up?  The best I could come up with was:
> 
> f2 <- function(n) {
>   if(is.null(n)){return(FALSE)}
>   if(is.na(n)){return(FALSE)}
>   if(abs(n) < pi) {
>     return(TRUE)
>   } else {
>     return(FALSE)
>   }
> }
> 
> This can't be the best way!  Anyway, f2() isn't right:
f2(numeric(0))
> fails; note that
> 
> R> if(is.na(numeric(0))){print("asdf")}
> 
> falls over.  help.search("trap") was not very helpful.  try()
doesn't
> help either:
> 
> R> try(if(1==NA){print("asdf")})
> Error in if (1 == NA) { : missing value where logical needed
> 
> 
> 
> QUESTION: how to make f() not give an error under any circumstances?
> 
> 
> 
> 
> 
> 
> -- 
> 
> Robin Hankin, Lecturer,
> School of Geography and Environmental Science
> Tamaki Campus
> Private Bag 92019 Auckland
> New Zealand
> 
> r.hankin at auckland.ac.nz
> tel 0064-9-373-7599 x6820; FAX 0064-9-373-7042
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help
> 
------------------------------------------------------------------------------

Robin Hankin

2003-Feb-14 00:30 UTC

head link

[R] generic handling of NA and NaN and NULL

Hi Spencer


thanks for this

> How about:
> 
>  > f3 <- function(n){
> +   n.pi <- (abs(n)<pi)
> +   n.pi[is.na(n.pi)] <- F
> +   n.pi
> + }
>  >

nope!

Sometimes I need things like

R> x <- 1:10
R> if(f3(x[x>11])==TRUE){print("asfd")}
Error in if (f3(x[x > 11]) == TRUE) { : missing value where logical needed



best


rksh





-- 

Robin Hankin, Lecturer,
School of Geography and Environmental Science
Tamaki Campus
Private Bag 92019 Auckland
New Zealand

r.hankin at auckland.ac.nz
tel 0064-9-373-7599 x6820; FAX 0064-9-373-7042

Robin Hankin

2003-Feb-14 00:33 UTC

head link

[R] generic handling of NA and NaN and NULL

Hello Andy

thanks for this; but


R> x <- 1:10
R> f
function(n) {
  if(is.null(n) || is.na(n) || abs(n) < pi) {
    return(FALSE)
  } else {
    return(TRUE)
  }
}
R> x <- 1:10
R> f(x[x>11])
Error in if (is.null(n) || is.na(n) || abs(n) < pi) { : 
	missing value where logical needed> 




> 
> Try:
> 
> f <- function(n) {
>   if(is.null(n) || is.na(n) || abs(n) < pi) {
>     return(FALSE)
>   } else {
>     return(TRUE)
>   }
> }
> 
> Note that the order of the conditions inside if() matters: is.na(n) only
> gets evaluated if is.null(n) is FALSE, and so on.
> 
> Andy
> 

-- 

Robin Hankin, Lecturer,
School of Geography and Environmental Science
Tamaki Campus
Private Bag 92019 Auckland
New Zealand

r.hankin at auckland.ac.nz
tel 0064-9-373-7599 x6820; FAX 0064-9-373-7042

Liaw, Andy

2003-Feb-14 00:36 UTC

head link

[R] generic handling of NA and NaN and NULL

> From: Spencer Graves [mailto:spencer.graves at pdf.com]
> 
> How about:
> 
>  > f3 <- function(n){
> +   n.pi <- (abs(n)<pi)
> +   n.pi[is.na(n.pi)] <- F
> +   n.pi
> + }
>  >
>  > f3(c(1, 5, NA))
> [1]  TRUE FALSE FALSE
>  >
A couple of problems: 

a) It chokes if argument is NULL.
b) Use of F instead of FALSE will not pass R CMD check, which is what Robin
wants.

Andy

 > Spencer Graves
> 
> Robin Hankin wrote:
> > Hello everybody
> > 
> > 
> > I have a generic problem which the following toy function 
> illustrates:
> > 
> > f <- function(n) {
> >   if(abs(n) < pi) {
> >     return(TRUE)
> >   } else {
> >     return(FALSE)
> >   }
> > }
> >                    
> > I want it to return TRUE if abs(n)<pi and FALSE otherwise.  f() is
> > fine as far as it goes, but does not deal well with NA or 
> NaN or NULL
> > (I want these to signal some problem with the argument (ie return
> > FALSE), but not to stop execution of f().  In particular, I want f()
> > to pass R CMD check )-:
> > 
> > R> f(NA)
> > Error in if (abs(n) < pi) { : missing value where logical needed
> > 
> > R> f(NULL)
> > Error in abs(n) : non-numeric argument to function
> > 
> > 
> > So, how best to patch f() up?  The best I could come up with was:
> > 
> > f2 <- function(n) {
> >   if(is.null(n)){return(FALSE)}
> >   if(is.na(n)){return(FALSE)}
> >   if(abs(n) < pi) {
> >     return(TRUE)
> >   } else {
> >     return(FALSE)
> >   }
> > }
> > 
> > This can't be the best way!  Anyway, f2() isn't right: 
> f2(numeric(0))
> > fails; note that
> > 
> > R> if(is.na(numeric(0))){print("asdf")}
> > 
> > falls over.  help.search("trap") was not very helpful.  
> try() doesn't
> > help either:
> > 
> > R> try(if(1==NA){print("asdf")})
> > Error in if (1 == NA) { : missing value where logical needed
> > 
> > 
> > 
> > QUESTION: how to make f() not give an error under any circumstances?
> > 
> > 
> > 
> > 
> > 
> >
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> http://www.stat.math.ethz.ch/mailman/listinfo/r-help
> 

------------------------------------------------------------------------------

Liaw, Andy

2003-Feb-14 00:40 UTC

head link

[R] generic handling of NA and NaN and NULL

The version I gave is obviously not vectorized (since your original version
seem to indicate that the argument won't have length > 1, otherwise the
if()
won't really make sense).

Replacing is.null(n) with length(n)!=1 (or length(n)==0) should do the trick
(I hope!).

Andy
> -----Original Message-----
> From: Robin Hankin [mailto:r.hankin at auckland.ac.nz]
> Sent: Thursday, February 13, 2003 6:30 PM
> To: andy_liaw at merck.com
> Cc: r.hankin at auckland.ac.nz; r-help at stat.math.ethz.ch
> Subject: Re: [R] generic handling of NA and NaN and NULL
> 
> 
> 
> 
> Hello Andy
> 
> thanks for this; but
> 
> 
> R> x <- 1:10
> R> f
> function(n) {
>   if(is.null(n) || is.na(n) || abs(n) < pi) {
>     return(FALSE)
>   } else {
>     return(TRUE)
>   }
> }
> R> x <- 1:10
> R> f(x[x>11])
> Error in if (is.null(n) || is.na(n) || abs(n) < pi) { : 
> 	missing value where logical needed
> > 
> 
> 
> 
> 
> 
> 
> > 
> > Try:
> > 
> > f <- function(n) {
> >   if(is.null(n) || is.na(n) || abs(n) < pi) {
> >     return(FALSE)
> >   } else {
> >     return(TRUE)
> >   }
> > }
> > 
> > Note that the order of the conditions inside if() matters: 
> is.na(n) only
> > gets evaluated if is.null(n) is FALSE, and so on.
> > 
> > Andy
> > 
> 
> 
> -- 
> 
> Robin Hankin, Lecturer,
> School of Geography and Environmental Science
> Tamaki Campus
> Private Bag 92019 Auckland
> New Zealand
> 
> r.hankin at auckland.ac.nz
> tel 0064-9-373-7599 x6820; FAX 0064-9-373-7042
> 

------------------------------------------------------------------------------

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