[R] cbind, data.frame | numeric to string?
R. Michael Weylandt
michael.weylandt at gmail.com
Tue Apr 10 18:04:02 CEST 2012
Sorry, I missed that the OP's real question was in character/factor,
not in the "why are these all factors" bit...good catch.
Rant about cbind() still stands though. :-) [Your way with cbind()
would give him all characters, not some characters and some numerics
since cbind() gives a matrix by default -- note that in Rainer's
construction, it doesn't coerce because it's giving a data.frame (as
cbind.data.frame does but cdbind.default doesn't) so no coercion is
necessary ]
Best,
Michael
On Tue, Apr 10, 2012 at 11:55 AM, Jessica Streicher
<j.streicher at micromata.de> wrote:
> Still didn't work for me without cbind , although you really don't need it ;)
>
> worked after i set options(stringsAsFactors=F).
>
>> options(stringsAsFactors=F)
>> df<-data.frame(intVec,chaVec)
>> df
> intVec chaVec
> 1 1 a
> 2 2 b
> 3 3 c
>
>> df$chaVec
> [1] "a" "b" "c"
>
> documentation of data.frame says the option is true by default.
>
>
> Am 10.04.2012 um 17:38 schrieb R. Michael Weylandt:
>
>> Don't use cbind() -- it forces everything into a single type, here
>> string, which in turn becomes factor.
>>
>> Simply,
>>
>> data.frame(a, b, c)
>>
>> Like David mentioned a few days ago, I have no idea who is promoting
>> this data.frame(cbind(...)) idiom, but it's a terrible idea (albeit
>> one that seems to be very frequent over the last few weeks)
>>
>> Michael
>>
>> On Tue, Apr 10, 2012 at 10:33 AM, Anser Chen <anser.chen at gmail.com> wrote:
>>> Complete newbie to R -- struggling with something which should be pretty
>>> basic. Trying to create a simple data set (which I gather R refers to as a
>>> data.frame). So
>>>
>>>> a <- c(1,2,3,4,5);
>>>> b <- c(0.3,0.4,0.5,0,6,0.7);
>>>
>>> Stick the two together into a data frame (call test) using cbind
>>>
>>>> test <- data.frame(cbind(a,b))
>>>
>>> Seems to do the trick:
>>>
>>>> test
>>> a b
>>> 1 1 0.3
>>> 2 2 0.4
>>> 3 3 0.5
>>> 4 4 0.6
>>> 5 5 0.7
>>>>
>>>
>>> Confirm that each variable is numeric:
>>>
>>>> is.numeric(test$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.
>
>
> [[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.
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