> On Nov 27, 2016, at 11:21 AM, Chris Evans <chrish...@psyctc.org> wrote:
>
> Was about to reply just to sender but thought there were good byproducts of
> this so, to all ...
>
> Many thanks Dr. Winsemius, and apologies for the HTML: tired sloppiness. My
> bad.
>
> Aha. For the first time I can really see a logic for dataFrame[['variable']]
> -- thanks for that. I will have to break myself of the "$" habit. Pity as
> it's a lot more keystrokes! W
>
> I understand about the nasty asset stripped side effects of cbind but thought
> in this situation it would cause no problems. Is the preferred route to
> create turn a first vector to data frame and then add the others using
> dataframe[['newVariable']] <- nextVector ?
With an existing dataframe the use of cbind is safe, because the cbind
data.frame function will not coerce arguments to matrix class. It is the use of
cbind with vectors that is the source of danger.
This would be the preferred method of constructing a data.frame from objects
with attributes:
dt <- as.Date( 1:10, origin="1970-01-01")
fac <- factor(letters[1:10])
nums <-10:1
dfrm <- data.frame( dt, fac, nums)
#OR skip the preliminary vector creation and use a named argument list:
dfrm <- data.frame( dt=as.Date( 1:10, origin="1970-01-01"),
fac=factor(letters[1:10]),
nums=10:1)
The second method lets you avoid leaving loose vectors that might later get
used inappropriately if you happened to later write a function with a parameter
or object that matched a named vector in the global environment.
After either method, you can `cbind` to that dfrm object to your heart's
content, because the cbind.data.frame method is dispatched.
--
David.
>
> Very best wishes and thanks again: this is an amazing list,
>
> Chris
>
>
> ----- Original Message -----
>> From: "David Winsemius" <dwinsem...@comcast.net>
>> To: "Chris Evans" <chrish...@psyctc.org>
>> Cc: r-help@r-project.org
>> Sent: Sunday, 27 November, 2016 18:25:18
>> Subject: Re: [R] In praise of "options(warnPartialMatchDollar = TRUE)"
>
>>> On Nov 27, 2016, at 7:12 AM, Chris Evans <chrish...@psyctc.org> wrote:
>>>
>>> I am just posting this to the list because someone else may one day waste an
>>> hour or so because s/he has unknowingly hit a partial match failure using
>>> "$".
>>> It's my folly that I did but I am surprised that
>>> options(warnPartialMatchDollar
>>> = TRUE) isn't the default setting.
>>>
>>> Here's a bit of reproducible code that shows the challenge.
>>>
>>> #rm(list=ls()) ### BEWARE: me making sure environment was clean
>>> set.seed(12345) # get fully reproducible example
>>> nRows <- 100
>>> Sample <- sample(0:1,nRows,replace=TRUE)
>>> data2 <- data.frame(cbind(1:nRows,Sample)) # create data frame
>>
>> Using dataframe( cbind( ...) ) is a predictable method for creating later
>> headaches. and there is no options-warning available. cbind coerces an
>> argument
>> list of vectors to matrix class, thus dropping all attributes (dates, times
>> and
>> factors are all destroyed.)
>>
>>> table(data2$Samp) # call which silently achieves partial match
>>> data2$innoccuousname <-
>>> factor(data2$Samp,labels=c("Non-clinical","Clinical"),levels=0:1)
>>> str(data2$Samp) # all fine, no apparent destruction of the non-existent
>>> vector
>>> data2$Samp
>>> data2$SampFac <-
>>> factor(data2$Samp,labels=c("Non-clinical","Clinical"),levels=0:1)
>>> str(data2$Samp) # returns NULL because there is no longer a single partial
>>> match
>>> to "Samp" but no warning!
>>> str(data2$Sample) # but of course, data2$Sample is still there
>>>
>>> Because I had used "data2$Samp" all the way through a large file of R
>>> (markup)
>>> code and hadn't noticed that the variable names in the SPSS file I was
>>> reading
>>> in had changed from "Samp" to "Sample" I appeared to be destroying
>>> data2$Samp.
>>>
>>> I have now set options(warnPartialMatchDollar = TRUE) in my Rprofile.site
>>> file
>>> and am just posting this here in case it helps someone some day.
>>
>> This is one of the reasons many experienced R programmers eschew the use of
>> the
>> "$" function in programming.
>>
>> The preferred use would be :
>>
>> data2[['Samp']]
>>
>> (No partial match.)
>>
>>>
>>> [[alternative HTML version deleted]]
>>
>> Plain text is generally preferred on Rhelp but there does not appear to have
>> been a problem in this posting instance.
>>
>>>
>>> ______________________________________________
>>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>> 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
>
> ______________________________________________
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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
______________________________________________
R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
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.
