[R] as.data.frame(cbind()) transforming numeric to factor?
Dear List, why does as.data.frame(cbind()) transform numeric variables to factors, once one of the other variablesused is a character vector? # x.1 - rnorm(10) x.2 - c(rep(Test,10)) Foo - as.data.frame(cbind(x.1)) is.factor(Foo$x.1) Foo - as.data.frame(cbind(x.1,x.2)) is.factor(Foo$x.1) # I assume there is a good reason for this, can somebody explain? Thanks. Best, Tom __ R-help@stat.math.ethz.ch 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] as.data.frame(cbind()) transforming numeric to factor?
On Fri, 2006-08-18 at 10:41 -0400, Tom Boonen wrote: Dear List, why does as.data.frame(cbind()) transform numeric variables to factors, once one of the other variablesused is a character vector? # x.1 - rnorm(10) x.2 - c(rep(Test,10)) Foo - as.data.frame(cbind(x.1)) is.factor(Foo$x.1) Foo - as.data.frame(cbind(x.1,x.2)) is.factor(Foo$x.1) # I assume there is a good reason for this, can somebody explain? Thanks. Best, Tom See the Note section of ?cbind, which states: The method dispatching is not done via UseMethod(), but by C-internal dispatching. Therefore, there is no need for, e.g., rbind.default. The dispatch algorithm is described in the source file (‘.../src/main/bind.c’) as 1. For each argument we get the list of possible class memberships from the class attribute. 2. We inspect each class in turn to see if there is an an applicable method. 3. If we find an applicable method we make sure that it is identical to any method determined for prior arguments. If it is identical, we proceed, otherwise we immediately drop through to the default code. If you want to combine other objects with data frames, it may be necessary to coerce them to data frames first. (Note that this algorithm can result in calling the data frame method if the arguments are all either data frames or vectors, and this will result in the coercion of character vectors to factors.) Thus, note the result of: str(cbind(x.1, x.2)) chr [1:10, 1:2] -0.265756038510064 2.13220714034528 ... - attr(*, dimnames)=List of 2 ..$ : NULL ..$ : chr [1:2] x.1 x.2 Since a matrix can only contain a single data type, the numeric vector is coerced to character. Then using as.data.frame() coerces the character matrix to factors, which is the default behavior. If you want to create a data frame, do it this way: str(data.frame(x.1, x.2)) `data.frame': 10 obs. of 2 variables: $ x.1: num -0.266 2.132 2.096 -0.128 -0.466 ... $ x.2: Factor w/ 1 level Test: 1 1 1 1 1 1 1 1 1 1 or if you want to retain the character vector, use I(): str(data.frame(x.1, I(x.2))) `data.frame': 10 obs. of 2 variables: $ x.1: num -0.266 2.132 2.096 -0.128 -0.466 ... $ x.2:Class 'AsIs' chr [1:10] Test Test Test Test ... See ?data.frame for more information. HTH, Marc Schwartz __ R-help@stat.math.ethz.ch 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] as.data.frame(cbind()) transforming numeric to factor?
On Fri, 18 Aug 2006, Tom Boonen wrote: Dear List, why does as.data.frame(cbind()) transform numeric variables to factors, once one of the other variablesused is a character vector? # x.1 - rnorm(10) x.2 - c(rep(Test,10)) Foo - as.data.frame(cbind(x.1)) is.factor(Foo$x.1) Foo - as.data.frame(cbind(x.1,x.2)) is.factor(Foo$x.1) # I assume there is a good reason for this, can somebody explain? Thanks. Only if you can explain the good reason why you did not just use data.frame(x.1, x.2)! cbind() makes a matrix out of vectors, here a character matrix. And then as.data.frame() converts character columns to factors. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UKFax: +44 1865 272595 __ R-help@stat.math.ethz.ch 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] as.data.frame(cbind()) transforming numeric to factor?
In R version 2.4.0 Under development (unstable) (2006-08-08 r38825) one can do this: as.data.frame(cbind(x.1,x.2),stringsAsFactors = FALSE) On 8/18/06, Tom Boonen [EMAIL PROTECTED] wrote: Dear List, why does as.data.frame(cbind()) transform numeric variables to factors, once one of the other variablesused is a character vector? # x.1 - rnorm(10) x.2 - c(rep(Test,10)) Foo - as.data.frame(cbind(x.1)) is.factor(Foo$x.1) Foo - as.data.frame(cbind(x.1,x.2)) is.factor(Foo$x.1) # I assume there is a good reason for this, can somebody explain? Thanks. Best, Tom __ R-help@stat.math.ethz.ch 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. __ R-help@stat.math.ethz.ch 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] as.data.frame(cbind()) transforming numeric to factor?
Thanks everybody. I recognize my mistake now. I think as.data.frame(cbind(x.1,x.2),stringsAsFactors = FALSE) would be a good idea. Tom On 8/18/06, Prof Brian Ripley [EMAIL PROTECTED] wrote: On Fri, 18 Aug 2006, Tom Boonen wrote: Dear List, why does as.data.frame(cbind()) transform numeric variables to factors, once one of the other variablesused is a character vector? # x.1 - rnorm(10) x.2 - c(rep(Test,10)) Foo - as.data.frame(cbind(x.1)) is.factor(Foo$x.1) Foo - as.data.frame(cbind(x.1,x.2)) is.factor(Foo$x.1) # I assume there is a good reason for this, can somebody explain? Thanks. Only if you can explain the good reason why you did not just use data.frame(x.1, x.2)! cbind() makes a matrix out of vectors, here a character matrix. And then as.data.frame() converts character columns to factors. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UKFax: +44 1865 272595 __ R-help@stat.math.ethz.ch 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] as.data.frame(cbind()) transforming numeric to factor?
Tom == Tom Boonen [EMAIL PROTECTED] on Fri, 18 Aug 2006 11:16:45 -0400 writes: Tom Thanks everybody. I recognize my mistake now. Tom I thinkas.data.frame(cbind(x.1,x.2),stringsAsFactors = FALSE) Tom would be a good idea. I think data.frame(x.1, x.2 = I(x.2)) would be a considerably better idea. [ The use of I(.) for preventing coercion to factors is a much older and S-like way ] Martin Tom Tom Tom On 8/18/06, Prof Brian Ripley [EMAIL PROTECTED] wrote: On Fri, 18 Aug 2006, Tom Boonen wrote: Dear List, why does as.data.frame(cbind()) transform numeric variables to factors, once one of the other variablesused is a character vector? # x.1 - rnorm(10) x.2 - c(rep(Test,10)) Foo - as.data.frame(cbind(x.1)) is.factor(Foo$x.1) Foo - as.data.frame(cbind(x.1,x.2)) is.factor(Foo$x.1) # I assume there is a good reason for this, can somebody explain? Thanks. Only if you can explain the good reason why you did not just use data.frame(x.1, x.2)! cbind() makes a matrix out of vectors, here a character matrix. And then as.data.frame() converts character columns to factors. -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UKFax: +44 1865 272595 Tom __ Tom R-help@stat.math.ethz.ch mailing list Tom https://stat.ethz.ch/mailman/listinfo/r-help Tom PLEASE do read the posting guide http://www.R-project.org/posting-guide.html Tom and provide commented, minimal, self-contained, reproducible code. __ R-help@stat.math.ethz.ch 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.
