R help - Oct 2005 - Warning: condition has length > 1

Hi -

I was wondering if anyone came across a problem such as mine! I was trying
to create a user-defined function, however, the results from calling the
function are unexpected!

When passing X parameter as a single value variable (x<-c(3)), everything
works fine. However, when passing a parameter as a vector with multiple
values (as the case in my code), the 'if condition' is only executed
once!

Here is my code:
> x
[1]  0.3  1.0  0.7 22.0
> myfunction<-function(x)
+ {
+ if (x>=1) 0
+ else x^2
+ }
> myfunction(x)
[1]   0.09   1.00   0.49 484.00
Warning message:
the condition has length > 1 and only the first element will be used in: if
(x >= 1) 0 else x^2 
>
Is there a way to overcome this issue? Can you please explain what
modifications to the code I need to accommodate to make it work.

Thanks,

Nawaf

nawaf b wrote:
> Hi -
> 
> I was wondering if anyone came across a problem such as mine! I was trying
> to create a user-defined function, however, the results from calling the
> function are unexpected!
> 
> When passing X parameter as a single value variable (x<-c(3)),
everything
> works fine. However, when passing a parameter as a vector with multiple
> values (as the case in my code), the 'if condition' is only
executed once!
> 
> Here is my code:
> 
>>x
> 
> [1]  0.3  1.0  0.7 22.0
> 
>>myfunction<-function(x)
> 
> + {
> + if (x>=1) 0
> + else x^2
> + }
?ifelse

myfunction <- function(x){ifelse(x >= 1, 0, x^2)}

 > myfunction(c(.3, 1, .7, 22))
[1] 0.09 0.00 0.49 0.00
>>myfunction(x)
> 
> [1]   0.09   1.00   0.49 484.00
> Warning message:
> the condition has length > 1 and only the first element will be used in:
if
> (x >= 1) 0 else x^2 
> 
> 
> Is there a way to overcome this issue? Can you please explain what
> modifications to the code I need to accommodate to make it work.
> 
> Thanks,
> 
> Nawaf
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> 
-- 
Chuck Cleland, Ph.D.
NDRI, Inc.
71 West 23rd Street, 8th floor
New York, NY 10010
tel: (212) 845-4495 (Tu, Th)
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fax: (917) 438-0894

ifelse(x >= 1, 0, x^2)

or

(x >= 1) * x^2

Also, you might need x > (1 - e) where e is some small number since your
numbers may not be exact.



On 10/8/05, nawaf b <talda at hotmail.com> wrote:
> Hi -
>
> I was wondering if anyone came across a problem such as mine! I was trying
> to create a user-defined function, however, the results from calling the
> function are unexpected!
>
> When passing X parameter as a single value variable (x<-c(3)),
everything
> works fine. However, when passing a parameter as a vector with multiple
> values (as the case in my code), the 'if condition' is only
executed once!
>
> Here is my code:
> > x
> [1]  0.3  1.0  0.7 22.0
> > myfunction<-function(x)
> + {
> + if (x>=1) 0
> + else x^2
> + }
> > myfunction(x)
> [1]   0.09   1.00   0.49 484.00
> Warning message:
> the condition has length > 1 and only the first element will be used in:
if
> (x >= 1) 0 else x^2
> >
>
> Is there a way to overcome this issue? Can you please explain what
> modifications to the code I need to accommodate to make it work.
>
> Thanks,
>
> Nawaf
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
>

On Sat, 8 Oct 2005, nawaf b wrote:
> Hi -
> 
> I was wondering if anyone came across a problem such as mine! I was trying
> to create a user-defined function, however, the results from calling the
> function are unexpected!
> 
> When passing X parameter as a single value variable (x<-c(3)),
everything
> works fine. However, when passing a parameter as a vector with multiple
> values (as the case in my code), the 'if condition' is only
executed once!
> 
> Here is my code:
> > x
> [1]  0.3  1.0  0.7 22.0
> > myfunction<-function(x)
> + {
> + if (x>=1) 0
> + else x^2
> + }
> > myfunction(x)
> [1]   0.09   1.00   0.49 484.00
> Warning message:
> the condition has length > 1 and only the first element will be used in:
if
> (x >= 1) 0 else x^2 
> >
> 
> Is there a way to overcome this issue? Can you please explain what
> modifications to the code I need to accommodate to make it work.
> myfunction<-function(x)
+ ifelse(x>=1, 0, x^2)
> x <- c(0.3, 1.0, 0.7, 22.0)
> myfunction(x)
[1] 0.09 0.00 0.49 0.00

ifelse() is vectorised, but if() only looks at the first element in x 
before deciding what to do - so if the condition is longer, the rest gets 
ignored.
> 
> Thanks,
> 
> Nawaf
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> 
-- 
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Helleveien 30, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43
e-mail: Roger.Bivand at nhh.no

nawaf b wrote:
> Hi -
> 
> I was wondering if anyone came across a problem such as mine! I was trying
> to create a user-defined function, however, the results from calling the
> function are unexpected!
> 
> When passing X parameter as a single value variable (x<-c(3)),
everything
> works fine. However, when passing a parameter as a vector with multiple
> values (as the case in my code), the 'if condition' is only
executed once!
> 
> Here is my code:
> 
>>x
> 
> [1]  0.3  1.0  0.7 22.0
> 
>>myfunction<-function(x)
> 
> + {
> + if (x>=1) 0
> + else x^2
> + }
> 
>>myfunction(x)
> 
> [1]   0.09   1.00   0.49 484.00
> Warning message:
> the condition has length > 1 and only the first element will be used in:
if
> (x >= 1) 0 else x^2 
> 
> 
> Is there a way to overcome this issue? Can you please explain what
> modifications to the code I need to accommodate to make it work.
I am going to go out on a limb here (I don't know much about R) but I'm 
not sure it has anything to do with that fact that you have defined a 
function.

It seems to me that "if (x > 1) {...}" expects a scalar and if x is
not
a scalar, it will use the first value.  To apply your function to each 
element, check out the help for sapply (eg ?sapply).  I am guessing the 
solution is something like sapply(x, myfunction) but don't quote me.

paul sorenson