Re: [R] Change case of factor in data frame
Ok, it seems that the function to get generic field names is get() res=names(dat); get(res[ind],pos=dat) will retrieve dat$name -- View this message in context: http://r.789695.n4.nabble.com/Change-case-of-factor-in-data-frame-tp4651696p4651919.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Change case of factor in data frame
On Dec 3, 2012, at 9:47 AM, Audrey wrote: Ok, it seems that the function to get generic field names is get() Er, not really. res=names(dat); get(res[ind],pos=dat) will retrieve dat$name There are far less baroque was of doing that (including dat$name and dat[[name]]. Read: ?[ If you had a numeric object, 'ind' then dat[ind] would retrieve a sub-list, with as many columns as there were items in 'ind' and would have class data.frame. If `ind` is numeric with one element only, then dat[[ind]] - tolower( as.character (dat[[ind]] ) ) # should succeed at least to the extent of returning a vector of a different class ... if what were what you wanted as to change . It would have been faster to change just the levels attributes for factor columns if you were willing to retain the class of that column as a factor. levels(dat[[1]])- toupper( levels(dat[[1]] ) -- David Winsemius, MD Alameda, CA, USA __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Change case of factor in data frame
On Dec 2, 2012, at 12:46 PM, Audrey wrote:
I am trying to write a function to change the case of all of the
text in a
data frame to lower case.
Define what you mean by text.
I do not have foreknowledge of the data frame
names or the data types of each column.
It seems that if one references the data frame by index, then it
returns
class data.frame but if it is referenced by name, it returns class
factor or whatever the column actually is:
dat[1] returns class data.frame but
dat$name returns class factor
Yes. That is correct.
The problem is that, when one applies the tolower() and toupper()
functions,
dat$name will return a column of lower/uppercase returns (now class
character) but dat[1] will return an array of factor level indexes.
It return an integer vector with attributes: class = factor and levels.
Specifying dat[1] as.character during the function call does not
work (e.g.
tolower(as.character(dat[1]))).
Because dat[1] is a list, not a vector.
So, I would loop over the column names, but I can not figure out how
to
generically call them:
tst=names(dat);
dat$(tst[1]) returns an error
dat[tst[1]] returns class data.frame again
Thank you in advance!
change_case-function(dat,wcase){
# change case
res=sapply(dat,class); # get classes
ind-res=='character';
dat[ind]-switch(wcase,
'lower'=tolower(dat[ind]),
'upper'=toupper(dat[ind])
)
rm(ind);
ind-res=='factor';
dat[ind]-switch(wcase,
'lower'=factor(tolower(as.character(dat[ind]))),
'upper'=factor(toupper(as.character(dat[ind])))
)
return(dat);
}
You probably need to study the help([) page and learn the difference
between [ and [[. Changing to [[ in a couple of places would
probably allow success.
--
David Winsemius, MD
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.
Re: [R] Change case of factor in data frame
res=names(dat); get(res[ind],pos=dat) will retrieve dat$name There are far less baroque was of doing that (including dat$name and dat[[name]]. Both dat$name and dat[[name]] require you to know what name is. I was looking for a way to retrieve a data frame column by name without actually knowing what the data frame column name was. get() seems to do that, but I am open to other options. Thank you for your advice regarding [ vs. [[. Indeed, lower(dat[[ind]]) does return the desired result. However, it seems that ind can only be a single integer (or evaluate to TRUE for only 1 column), I guess because [[ is returning a vector. By text I mean anything that was non-numerical: character and factor classes, in my case. -- View this message in context: http://r.789695.n4.nabble.com/Change-case-of-factor-in-data-frame-tp4651696p4651971.html Sent from the R help mailing list archive at Nabble.com. __ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Re: [R] Change case of factor in data frame
On Dec 3, 2012, at 3:34 PM, Audrey wrote: res=names(dat); get(res[ind],pos=dat) will retrieve dat$name There are far less baroque was of doing that (including dat$name and dat[[name]]. Both dat$name and dat[[name]] require you to know what name is. I was looking for a way to retrieve a data frame column by name without actually knowing what the data frame column name was. get() seems to do that, but I am open to other options. And I gave you some, but you failed to include context, an annoying habit of Nabble users. (In my opinion the Nabble interface is more hassle than it is worth.) For instance, I wrote: If you had a numeric object, 'ind' then dat[ind] would retrieve a sub-list, with as many columns as there were items in 'ind' and would have class data.frame. Thank you for your advice regarding [ vs. [[. Indeed, lower(dat[[ind]]) does return the desired result. However, it seems that ind can only be a single integer That was what I wrote I believe. (or evaluate to TRUE for only 1 column), In some instances TRUE is coerced to 1. I guess because [[ is returning a vector. No. You have failed to understand that [[ can only return a single referenced object. It might be a vector or a list, but you cannot give it a vector with more than one element and expect satisfactory results. By text I mean anything that was non-numerical: character and factor classes, in my case. Then you should be clear. text is not a well defined term when referring to R objects. View this message in context: http://r.789695.n4.nabble.com/Change-case-of-factor-in-data-frame-tp4651696p4651971.html Sent from the R help mailing list archive at Nabble.com. No. This borders on actionable fraud. R-help is not Nabble. Do not believe what Nabble is saying. Do read the Rhelp Posting Guide. -- David Winsemius, MD 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.
