So how would I get the following to work?
> aa<-1
> aa
[1] 1
> 'foo<-' <- function(x,value) x<-value
> foo(aa)<-1:10
> aa
[1] 1 2 3 4 5 6 7 8 9 10
> # This doesn't work:
> foo(aa)[4:5] <- c(101,102)
Error in foo(aa)[4:5] <- c(101, 102) : could not find function "foo"
> # What I would like to see is: aa becomes 1 2 3 101 102 6 7 8 9 10
> # Is it possible to define such a function 'foo'?
Sent from my iPhone
On Jul 10, 2013, at 4:10 PM, Bert Gunter <gunter.ber...@gene.com> wrote:
I think the OP may perhaps want to define a method for "[<-" .
e.g. try:
methods("[<-")
If this is not it ... ??
Cheers,
Bert
On Wed, Jul 10, 2013 at 12:51 PM, David Winsemius
<dwinsem...@comcast.net> wrote:
>
> On Jul 10, 2013, at 12:17 PM, Harry Mamaysky wrote:
>
>> As I understand it rownames(aa) returns a copy of an attribute of aa. So
>> changing the value of this vector should make the change to the copy of the
>> row.names attribute. I would then have to set the original row.names equal
>> to this copy to effect the change.
>>
>> So my question is why "rownames(aa)[2:4] <-" changes the original attribute
>> rather than its copy?
>
> I'm not sure how you decide that was happening. Your first paragraph seemed
> correct:
>
> aa <- data.frame( a=1:10,b=101:110 )
> str(aa)
> attributes(aa)
> dput(aa)
> `rownames<-`
>
>> trace(`rownames<-`)
>> rownames(aa)[2:4] <- c('row2','row3','row4')
> trace: `rownames<-`(`*tmp*`, value = c("1", "row2", "row3", "row4",
> "5", "6", "7", "8", "9", "10"))
>
> You can see that R first builds a full length vector with the second argumens
> to `rownames<-` fully expanded before doing the assignment to the 'row.names'
> attribute.
>
>>
>> And the follow on question is whether it's possible to have "f(x)[2:4] <-"
>> operate in the same way for some user defined replacement function f.
>
> Take a look at the code:
>
> `row.names<-.data.frame`
>
> --
> David.
>>
>> Sent from my iPhone
>>
>> On Jul 10, 2013, at 3:05 PM, David Winsemius <dwinsem...@comcast.net> wrote:
>>
>>
>> On Jul 10, 2013, at 11:47 AM, Harry Mamaysky wrote:
>>
>>> I know how to define replacement functions in R (i.e. âfoo<-â <-
>>> function(x,value) x<-value, etc.), but how do you define replacement
>>> functions that operate on subsets of arrays (i.e. how do you pass an index
>>> into foo)?
>>> For example, why does the following use of ârownamesâ work?
>>
>> `rownames` of a dataframe is a vector, so indexing with "[" and a single
>> vector of indices is adequate. I cannot really tell what your conceptual
>> "why"-difficulty might be. This is just assignment within a vector. That is
>> not really a "replacement function operating on a subset of an array" since
>> rownames are not values of the dataframe .... and it's not an "array".
>> (Careful use of terms is needed here.)
>>
>>
>>>
>>>> aa <- data.frame( a=1:10,b=101:110 )
>>>
>>>> aa
>>>
>>> a b
>>>
>>> 1 1 101
>>>
>>> 2 2 102
>>>
>>> 3 3 103
>>>
>>> 4 4 104
>>>
>>> 5 5 105
>>>
>>> 6 6 106
>>>
>>> 7 7 107
>>>
>>> 8 8 108
>>>
>>> 9 9 109
>>>
>>> 10 10 110
>>>
>>>> rownames(aa)[2:4] <- c('row2','row3','row4')
>>>
>>>> aa
>>>
>>> a b
>>>
>>> 1 1 101
>>>
>>> row2 2 102
>>>
>>> row3 3 103
>>>
>>> row4 4 104
>>>
>>> 5 5 105
>>>
>>> 6 6 106
>>>
>>> 7 7 107
>>>
>>> 8 8 108
>>>
>>> 9 9 109
>>>
>>> 10 10 110
>>>
>>>
>>>
>>>
>>> Thanks,
>>>
>>> Harry
>>>
>>>
>>> [[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-help@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
>> Alameda, CA, USA
>
> David Winsemius
> Alameda, CA, USA
>
> ______________________________________________
> R-help@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
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