[R] cbind, data.frame | numeric to string?

[Rainer Schuermann]

cbind() works as well, but only if c is attached to the existing test variable:

> tst <- cbind( test, c )                                                                          
> tst                                                                                              
   a    b   c                                                                                       
1  1  0.3  y1                                                                                       
2  2  0.4  y2                                                                                       
3  3  0.5  y3                                                                                       
4  4  0.6  y4                                                                                       
5  5  0.7  y5                                                                                       
> str( tst )                                                                          
'data.frame':   5 obs. of  3 variables:                                                          
 $ a: num  1 2 3 4 5                                                                             
 $ b: num  0.3 0.4 0.5 0.6 0.7                                                                   
 $ c: Factor w/ 5 levels "y1","y2","y3",..: 1 2 3 4 5

Not saying it is a good idea, though...

Rainer


On Tuesday 10 April 2012 11:38:51 R. Michael Weylandt wrote:
> Don't use cbind() -- it forces everything into a single type, here
> string, which in turn becomes factor.
> 
> Simply,
> 
> data.frame(a, b, c)
> 
> Like David mentioned a few days ago, I have no idea who is promoting
> this data.frame(cbind(...)) idiom, but it's a terrible idea (albeit
> one that seems to be very frequent over the last few weeks)
> 
> Michael
> 
> On Tue, Apr 10, 2012 at 10:33 AM, Anser Chen <anser.chen at gmail.com> wrote:
> > Complete newbie to R -- struggling with something which should be pretty
> > basic. Trying to create a simple data set (which I gather R refers to as a
> > data.frame). So
> >
> >>  a <- c(1,2,3,4,5);
> >>  b <- c(0.3,0.4,0.5,0,6,0.7);
> >
> > Stick the two together into a data frame (call test) using cbind
> >
> >> test <- data.frame(cbind(a,b))
> >
> > Seems to do the trick:
> >
> >> test
> >  a   b
> > 1 1 0.3
> > 2 2 0.4
> > 3 3 0.5
> > 4 4 0.6
> > 5 5 0.7
> >>
> >
> > Confirm that each variable is numeric:
> >
> >> is.numeric(test$a)
> > [1] TRUE
> >> is.numeric(test$b)
> > [1] TRUE
> >
> >
> > OK, so far so good. But, now I want to merge in a vector of characters:
> >
> >> c <- c('y1","y2","y3","y4","y5")
> >
> > Confirm that this is string:
> >
> >> is.numeric(c);
> > [1] FALSE
> >
> > cbind c into the data frame:
> >
> >>  test <- data.frame(cbind(a,b,c))
> >
> > Looks like everything is in place:
> >
> >> test
> >  a   b  c
> > 1 1 0.3 y1
> > 2 2 0.4 y2
> > 3 3 0.5 y3
> > 4 4 0.6 y4
> > 5 5 0.7 y5
> >
> > Except that it seems as if the moment I cbind in a character vector, it
> > changes numeric data to string:
> >
> >> is.numeric(test$a)
> > [1] FALSE
> >> is.numeric(test$b)
> > [1] FALSE
> >
> > which would explain why the operations I'm trying to perform on elements of
> > a and b columns are failing. If I look at the structure of the data.frame,
> > I see that in fact *all* the variables are being entered as "factors".
> >
> >> str(test)
> > 'data.frame':   5 obs. of  3 variables:
> >  $ a: Factor w/ 5 levels "1","2","3","4",..: 1 2 3 4 5
> >  $ b: Factor w/ 5 levels "0.3","0.4","0.5",..: 1 2 3 4 5
> >  $ c: Factor w/ 5 levels "y1","y2","y3",..: 1 2 3 4 5
> >
> > But, if I try
> >
> >  test <- data.frame(cbind(a,b))
> >> str(test)
> > 'data.frame':   5 obs. of  2 variables:
> >  $ a: num  1 2 3 4 5
> >  $ b: num  0.3 0.4 0.5 0.6 0.7
> >
> > a and b are coming back as numeric. So, why does cbind'ing a column of
> > character variables change everything else? And, more to the point, what do
> > I need to do to 'correct' the problem (i.e., stop this from happening).
> >
> >        [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help at 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.
> 
> ______________________________________________
> R-help at 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.