[R] Concatenate a Variable

[Marc Schwartz]

Carla Rebelo wrote:
> Good morning!
> 
> I do not speak English very well and so I will try to explain the best I 
> can. I have this:
> 
>  > tabela[,1]
> [1] a a b b a c b a c c c c c
> Levels: a b c
> 
>  >unique(tabela[,1])
> [1] a b c
> Levels: a b c
> 
>  >var<-unique(tabela[,1])[1]
> 
>  > var
> [1] a
> Levels: a b c
> 
> But if I concatenate like this
>  > cat("VAR: ", var, "\n")
> 
> I obtain
>  >VAR:  1
> 
> and I want to obtain
>  >VAR: a
> 
> How can I do this? Thanks!

'a' is a factor, thus you are getting the underlying numeric code as the
output.

Note from ?cat:

Currently only atomic vectors (and so not lists) and names are handled.
Character strings are output ‘as is’ (unlike print.default which escapes
non-printable characters and backslash — use encodeString if you want to
output encoded strings using cat). Other types of R object should be
converted (e.g. by as.character or format) before being passed to cat.


Thus:

var <- factor("a", levels = c("a", "b", "c"))

> var
[1] a
Levels: a b c

> is.vector(var)
[1] FALSE


So 'var' is not an atomic vector and you must therefore coerce it to a
character vector using as.character() before passing it to cat():

> cat("VAR: ", as.character(var), "\n")
VAR:  a


HTH,

Marc Schwartz