cbind, data.frame | numeric to string?

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).

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