[R] extract printed value from a function

[David Winsemius]

On Feb 24, 2011, at 10:07 AM, Peter Ehlers wrote:

> On 2011-02-24 06:32, David Winsemius wrote:
>>
>> On Feb 24, 2011, at 7:22 AM, Peter Ehlers wrote:
>>
>>> On 2011-02-24 03:26, Duarte Viana wrote:
>>>> Hello all,
>>>>
>>>> This shouldn't be difficult, but I am not able to extract a printed
>>>> value from a function and assign it to an object.
>>>>
>>>> In my case,
>>>>
>>>>> library(DAAG)
>>>>> twotPermutation(c(2,3,4),c(3,6,5),plotit=F)
>>>> [1] 0.298
>>>>
>>>> I would like to assign this result to an object.
>>
>> A third suggestion which has virtues of simplicity and keeping the
>> result "numeric":
>>
>> x<- print( twotPermutation(c(2,3,4),c(3,6,5),plotit=F) )
>
> Does that work? Not for me.

Sorry. Not for me either. I had assumed from your comments about the  
use of invisible that the value was returned in invisible() but see  
now that you were being more specific. The author is effectively  
blanking the result and the help page is misleading when stating that  
the p-value is the "Value". He would be more accurate if stating that  
the p-value is printed as a side effect but that no value is returned.

>>
>>  >  x
>> [1] 0.1
>
> This may be some 'other' x. DAAG's twotPermutation() has an
> explicit
>
>  print(signif(pval, 3))
>
> as its penultimate statement, followed by
>
>  invisible()
>
> I don't know what, if any, advantage this code has over simply
> returning
>
>  invisible(signif(pval, 3))
>
> Peter Ehlers
>
>>  >  x<- print(invisible (0.2))
>> [1] 0.2
>>  >  x
>> [1] 0.2
>>
>> --
>>
>>
>>>
>>> Two suggestions:
>>> 1.
>>> Modify the code for twotPermutation by removing the invisible()
>>> at the end.
>>>
>>> 2.
>>> Use capture.output to capture the result and then convert
>>> to numeric:
>>>
>>> pvstring<- capture.output(
>>>     twotPermutation( c(2,3,4), c(3,6,5), plotit=FALSE) ))
>>>
>>> Now you can use strsplit or substr to extract the numeric part:
>>>
>>> pv<- as.numeric(strsplit(pvstring, " ")[[1]][2])
>>>
>>> or
>>>
>>> pv<- as.numeric(
>>>      substr(pvstring, nchar(pvstring) - 5, nchar(pvstring)))
>>>
>>> Peter Ehlers
>>>
>>>>
>>>> Thanks,
>>>>
>>>> Duarte
>>>>
>>>> ______________________________________________
>>>> 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.
>>
>> David Winsemius, MD
>> West Hartford, CT
>>
>

David Winsemius, MD
West Hartford, CT