> On Dec 5, 2016, at 9:53 AM, Rui Barradas <ruipbarra...@sapo.pt> wrote:
>
> Hello,
>
> Inline.
>
> Em 05-12-2016 17:09, David Winsemius escreveu:
>>
>>> On Dec 5, 2016, at 7:29 AM, John Sorkin <jsor...@grecc.umaryland.edu> wrote:
>>>
>>> Rui,
>>> I appreciate your suggestion, but eliminating the deparse statement does
>>> not solve my problem. Do you have any other suggestions? See code below.
>>> Thank you,
>>> John
>>>
>>>
>>> mydf <-
>>> data.frame(id=c(1,2,3,4,5),sex=c("M","M","M","F","F"),age=c(20,34,43,32,21))
>>> mydf
>>> class(mydf)
>>>
>>>
>>> myfun <- function(frame,var){
>>> call <- match.call()
>>> print(call)
>>>
>>>
>>> indx <- match(c("frame","var"),names(call),nomatch=0)
>>> print(indx)
>>> if(indx[1]==0) stop("Function called without sufficient arguments!")
>>>
>>>
>>> cat("I can get the name of the dataframe as a text string!\n")
>>> #xx <- deparse(substitute(frame))
>>> print(xx)
>>>
>>>
>>> cat("I can get the name of the column as a text string!\n")
>>> #yy <- deparse(substitute(var))
>>> print(yy)
>>>
>>>
>>> # This does not work.
>>> print(frame[,var])
>>>
>>>
>>> # This does not work.
>>> print(frame[,"var"])
>>>
>>>
>>>
>>>
>>> # This does not work.
>>> col <- xx[,"yy"]
>>>
>>>
>>> # Nor does this work.
>>> col <- xx[,yy]
>>> print(col)
>>> }
>>>
>>>
>>> myfun(mydf,age)
>>
>>
>> When you use that calling syntax, the system will supply the values of
>> whatever the `age` variable contains. (And if there is no `age`-named
>> object, you get an error at the time of the call to `myfun`.
>
> Actually, no, which was very surprising to me but John's code worked (not the
> function, the call). And with the change I've proposed, it worked flawlessly.
> No errors. Why I don't know.
I see. Must be one of those "promise" things. It appears that if you don't
actually require the value you can just pass a name with no value?
Thanks for the correction.
--
David.
>
> Rui Barradas
>
> You need either to call it as:
>>
>> myfun( mydf , "age")
>>
>>
>> # Or:
>>
>> age <- "age"
>> myfun( mydf, age)
>>
>> Unless your value of the `age`-named variable was "age" in the calling
>> environment (and you did not give us that value in either of your postings),
>> you would fail.
>>
David Winsemius
Alameda, CA, USA
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