Argument validation within functions - R-help

Tue, Dec 6, 2011 4:57 AM #

Use the ! (not) operator.

Not sure what you mean by " as the stop() stops the total function":
try the following

f <- function(a){
? ?stopifnot(a > 3)
? ?return(a^2)
}

f(2)
f(4)

Michael

(PS -- It's usually asked to cc the list so that this all gets
threaded properly in folks' mailboxes)

On Tue, Dec 6, 2011 at 7:46 AM, Johannes Radinger <JRadinger at gmx.at> wrote:

Hi,

thank you... I think I will go for the if-stop approach
as the stop() stops the total function... So there is just
one little other question: What is the opposite of is.numeric?
Is ther isnot.numeric? How ?can that be implemented in following
function:

f <- function(a){
? ? ? ?if(is.numeric(a)) stop("a is not numeric")
? ? ? ?if(0 > a && a > 1) stop("a must be a value between 0 and 1")
? ? ? ?a
}

/Johannes

-------- Original-Nachricht --------

Datum: Tue, 6 Dec 2011 07:04:59 -0500
Von: "R. Michael Weylandt" <michael.weylandt at gmail.com>
An: Johannes Radinger <JRadinger at gmx.at>
CC: r-help at r-project.org
Betreff: Re: [R] Argument validation within functions

The quick and dirty way to do so is to use: stopifnot() in conjunction
(if necessary with all() and any()). You can replace that first
condition with a simple is.numeric() as well. A more helpful way (if
this is production code) is to use if statement with the stop()
function directly which lets you provide specific error messages.

Michael

On Tue, Dec 6, 2011 at 6:41 AM, Johannes Radinger <JRadinger at gmx.at>
wrote:

Hi,

I just started with writing functions in R and so some questions popped

up.

I provide some values as argument to my function such as:

function(a,b,c){}

Now i want that the function first checks if the arguments are valid for

the function. E.g argument "a" has to be a number in the range 0-1. How
can that easily done?

So far I have:

? ? ? ?a <- as.numeric(a)
? ? ? ?if(0 <= a && a <= 1)

to first check if a is a number...if not the function stops and gives an

error message. If it is a number it just continues...

But how to check the range?
Above there is the if-approach but then the rest of the function is

exectued as part of if (or else). Is there a simpler way without having the
if-brackets around the remaining code?

Just a check if the value is between 0 and 1 and if yes continue with

the next line if no abort the function with a error message? How can such an
error message be created?

thank you and best regards,

/Johannes
--

______________________________________________
R-help at r-project.org 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.

Johannes Radinger

Tue, Dec 6, 2011 7:15 AM #

Thank you, i didn't know that the !operator is
also working for is.numeric etc.

Anyway I want to test if an argument is set in the
function call and if not a code is executed... So 
far I tried:

f <-function(a,b){
	if(!exists("b")) print("exists: b is not set")
	if(is.null("b")) print("is.null : b is not set")
}

f(a=1,b=2)
f(a=1)
f(b=2)

I don't really know how to do it...e.g: for f(a=1) b is not set
so it also can't be NULL (thats why is.null is not working). I
just want to "test" if it is set with the function call not outside
the function or before etc.

/Johannes

-------- Original-Nachricht --------

Datum: Tue, 6 Dec 2011 07:57:44 -0500
Von: "R. Michael Weylandt" <michael.weylandt at gmail.com>
An: r-help <r-help at r-project.org>, Johannes Radinger <JRadinger at gmx.at>
Betreff: Re: [R] Argument validation within functions

Use the ! (not) operator.

Not sure what you mean by " as the stop() stops the total function":
try the following

f <- function(a){
? ?stopifnot(a > 3)
? ?return(a^2)
}

f(2)
f(4)

Michael

(PS -- It's usually asked to cc the list so that this all gets
threaded properly in folks' mailboxes)

On Tue, Dec 6, 2011 at 7:46 AM, Johannes Radinger <JRadinger at gmx.at>
wrote:

Hi,

thank you... I think I will go for the if-stop approach
as the stop() stops the total function... So there is just
one little other question: What is the opposite of is.numeric?
Is ther isnot.numeric? How ?can that be implemented in following
function:

f <- function(a){
? ? ? ?if(is.numeric(a)) stop("a is not numeric")
? ? ? ?if(0 > a && a > 1) stop("a must be a value between 0 and 1")
? ? ? ?a
}

/Johannes

-------- Original-Nachricht --------

Datum: Tue, 6 Dec 2011 07:04:59 -0500
Von: "R. Michael Weylandt" <michael.weylandt at gmail.com>
An: Johannes Radinger <JRadinger at gmx.at>
CC: r-help at r-project.org
Betreff: Re: [R] Argument validation within functions

The quick and dirty way to do so is to use: stopifnot() in conjunction
(if necessary with all() and any()). You can replace that first
condition with a simple is.numeric() as well. A more helpful way (if
this is production code) is to use if statement with the stop()
function directly which lets you provide specific error messages.

Michael

On Tue, Dec 6, 2011 at 6:41 AM, Johannes Radinger <JRadinger at gmx.at>
wrote:

Hi,

I just started with writing functions in R and so some questions

popped

up.

I provide some values as argument to my function such as:

function(a,b,c){}

Now i want that the function first checks if the arguments are valid

for

the function. E.g argument "a" has to be a number in the range 0-1. How
can that easily done?

So far I have:

? ? ? ?a <- as.numeric(a)
? ? ? ?if(0 <= a && a <= 1)

to first check if a is a number...if not the function stops and gives

an

error message. If it is a number it just continues...

But how to check the range?
Above there is the if-approach but then the rest of the function is

exectued as part of if (or else). Is there a simpler way without having

the

if-brackets around the remaining code?

Just a check if the value is between 0 and 1 and if yes continue with

the next line if no abort the function with a error message? How can

such an

error message be created?

thank you and best regards,

/Johannes
--

______________________________________________
R-help at r-project.org 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.

--

Berwin A Turlach

Tue, Dec 6, 2011 7:36 AM #

G'day Johannes,

On Tue, 06 Dec 2011 16:15:21 +0100

"Johannes Radinger" <JRadinger at gmx.at> wrote:

?missing

Cheers,
	
	Berwin

========================== Full address ============================
A/Prof Berwin A Turlach               Tel.: +61 (8) 6488 3338 (secr)
School of Maths and Stats (M019)            +61 (8) 6488 3383 (self)
The University of Western Australia   FAX : +61 (8) 6488 1028
35 Stirling Highway                   
Crawley WA 6009                e-mail: Berwin.Turlach at gmail.com
Australia                        http://www.maths.uwa.edu.au/~berwin

Enrico Schumann

Tue, Dec 6, 2011 7:39 AM #

you may be looking for ?missing

f <- function(a,b) {
     if (missing(b)) print("b is missing")
}

f(a=1, b=2)
f(a=1)
f(b=2)

Regards,
Enrico

Am 06.12.2011 16:15, schrieb Johannes Radinger:

Thank you, i didn't know that the !operator is
also working for is.numeric etc.

Anyway I want to test if an argument is set in the
function call and if not a code is executed... So
far I tried:

f<-function(a,b){
	if(!exists("b")) print("exists: b is not set")
	if(is.null("b")) print("is.null : b is not set")
}

f(a=1,b=2)
f(a=1)
f(b=2)

I don't really know how to do it...e.g: for f(a=1) b is not set
so it also can't be NULL (thats why is.null is not working). I
just want to "test" if it is set with the function call not outside
the function or before etc.

/Johannes

-------- Original-Nachricht --------

Datum: Tue, 6 Dec 2011 07:57:44 -0500
Von: "R. Michael Weylandt"<michael.weylandt at gmail.com>
An: r-help<r-help at r-project.org>, Johannes Radinger<JRadinger at gmx.at>
Betreff: Re: [R] Argument validation within functions

Use the ! (not) operator.

Not sure what you mean by " as the stop() stops the total function":
try the following

f<- function(a){
    stopifnot(a>  3)
    return(a^2)
}

f(2)
f(4)

Michael

(PS -- It's usually asked to cc the list so that this all gets
threaded properly in folks' mailboxes)

On Tue, Dec 6, 2011 at 7:46 AM, Johannes Radinger<JRadinger at gmx.at>
wrote:

Hi,

thank you... I think I will go for the if-stop approach
as the stop() stops the total function... So there is just
one little other question: What is the opposite of is.numeric?
Is ther isnot.numeric? How  can that be implemented in following
function:

f<- function(a){
        if(is.numeric(a)) stop("a is not numeric")
        if(0>  a&&  a>  1) stop("a must be a value between 0 and 1")
        a
}

/Johannes

-------- Original-Nachricht --------

Datum: Tue, 6 Dec 2011 07:04:59 -0500
Von: "R. Michael Weylandt"<michael.weylandt at gmail.com>
An: Johannes Radinger<JRadinger at gmx.at>
CC: r-help at r-project.org
Betreff: Re: [R] Argument validation within functions

The quick and dirty way to do so is to use: stopifnot() in conjunction
(if necessary with all() and any()). You can replace that first
condition with a simple is.numeric() as well. A more helpful way (if
this is production code) is to use if statement with the stop()
function directly which lets you provide specific error messages.

Michael

On Tue, Dec 6, 2011 at 6:41 AM, Johannes Radinger<JRadinger at gmx.at>
wrote:

Hi,

I just started with writing functions in R and so some questions

popped

up.

I provide some values as argument to my function such as:

function(a,b,c){}

Now i want that the function first checks if the arguments are valid

for

the function. E.g argument "a" has to be a number in the range 0-1. How
can that easily done?

So far I have:

        a<- as.numeric(a)
        if(0<= a&&  a<= 1)

to first check if a is a number...if not the function stops and gives

an

error message. If it is a number it just continues...

But how to check the range?
Above there is the if-approach but then the rest of the function is

exectued as part of if (or else). Is there a simpler way without having

the

if-brackets around the remaining code?

Just a check if the value is between 0 and 1 and if yes continue with

the next line if no abort the function with a error message? How can

such an

error message be created?

thank you and best regards,

/Johannes
--

______________________________________________
R-help at r-project.org 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.

______________________________________________
R-help at r-project.org 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.

Enrico Schumann
Lucerne, Switzerland
http://nmof.net/

Bert Gunter

Tue, Dec 6, 2011 8:05 AM #

On Tue, Dec 6, 2011 at 7:15 AM, Johannes Radinger <JRadinger at gmx.at> wrote:

Read (more carefully?) R docs, please. ! is a unary function that
takes a logical argument(and will coerce to logical nonlogical
arguments if it can); is.numeric() returns a logical, so of course it
should "work". Ergo your failure to understand indicates a fundamental
hole in your understanding of how R works.

-- Bert

Anyway I want to test if an argument is set in the
function call and if not a code is executed... So
far I tried:

f <-function(a,b){
? ? ? ?if(!exists("b")) print("exists: b is not set")
? ? ? ?if(is.null("b")) print("is.null : b is not set")
}

f(a=1,b=2)
f(a=1)
f(b=2)

I don't really know how to do it...e.g: for f(a=1) b is not set
so it also can't be NULL (thats why is.null is not working). I
just want to "test" if it is set with the function call not outside
the function or before etc.

/Johannes

-------- Original-Nachricht --------

Datum: Tue, 6 Dec 2011 07:57:44 -0500
Von: "R. Michael Weylandt" <michael.weylandt at gmail.com>
An: r-help <r-help at r-project.org>, Johannes Radinger <JRadinger at gmx.at>
Betreff: Re: [R] Argument validation within functions

Use the ! (not) operator.

Not sure what you mean by " as the stop() stops the total function":
try the following

f <- function(a){
? ?stopifnot(a > 3)
? ?return(a^2)
}

f(2)
f(4)

Michael

(PS -- It's usually asked to cc the list so that this all gets
threaded properly in folks' mailboxes)

On Tue, Dec 6, 2011 at 7:46 AM, Johannes Radinger <JRadinger at gmx.at>
wrote:

Hi,

thank you... I think I will go for the if-stop approach
as the stop() stops the total function... So there is just
one little other question: What is the opposite of is.numeric?
Is ther isnot.numeric? How ?can that be implemented in following
function:

f <- function(a){
? ? ? ?if(is.numeric(a)) stop("a is not numeric")
? ? ? ?if(0 > a && a > 1) stop("a must be a value between 0 and 1")
? ? ? ?a
}

/Johannes

-------- Original-Nachricht --------

Datum: Tue, 6 Dec 2011 07:04:59 -0500
Von: "R. Michael Weylandt" <michael.weylandt at gmail.com>
An: Johannes Radinger <JRadinger at gmx.at>
CC: r-help at r-project.org
Betreff: Re: [R] Argument validation within functions

The quick and dirty way to do so is to use: stopifnot() in conjunction
(if necessary with all() and any()). You can replace that first
condition with a simple is.numeric() as well. A more helpful way (if
this is production code) is to use if statement with the stop()
function directly which lets you provide specific error messages.

Michael

On Tue, Dec 6, 2011 at 6:41 AM, Johannes Radinger <JRadinger at gmx.at>
wrote:

Hi,

I just started with writing functions in R and so some questions

popped

up.

I provide some values as argument to my function such as:

function(a,b,c){}

Now i want that the function first checks if the arguments are valid

for

the function. E.g argument "a" has to be a number in the range 0-1. How
can that easily done?

So far I have:

? ? ? ?a <- as.numeric(a)
? ? ? ?if(0 <= a && a <= 1)

to first check if a is a number...if not the function stops and gives

an

error message. If it is a number it just continues...

But how to check the range?
Above there is the if-approach but then the rest of the function is

exectued as part of if (or else). Is there a simpler way without having

the

if-brackets around the remaining code?

Just a check if the value is between 0 and 1 and if yes continue with

the next line if no abort the function with a error message? How can

such an

error message be created?

thank you and best regards,

/Johannes
--

______________________________________________
R-help at r-project.org 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.

______________________________________________
R-help at r-project.org 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.

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm