> 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.
>
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David Winsemius
Alameda, CA, USA
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