[R] How can I improve an ugly, dumb hack

[Eik Vettorazzi]

Hi Bert,
maybe I'm missing the point, but

dd<-cbind(d,m)

does 1, 2 and 3 as desired:

n <- data.frame(nx=letters[7:9], ny = 7:9)
str(cbind(d,m,n))

t<-letters[7:9]
str(cbind(d,t))

cheers.


Am 06.09.2012 18:03, schrieb Bert Gunter:
> Hi Folks:
> 
> Here's the situation:
> 
>> m <- cbind(x=letters[1:3], y = letters[4:6])
>> m
>      x   y
> [1,] "a" "d"
> [2,] "b" "e"
> [3,] "c" "f"
> 
> ## m is a 2 column character matrix
> 
>> d <- data.frame(a=1:3,b=4:6)
>> d$c <- m
>> d
>   a b c.x c.y
> 1 1 4   a   d
> 2 2 5   b   e
> 3 3 6   c   f
> 
> ## But please note (as was remarked in a thread here a couple of months ago)
>> ncol(d)
> [1] 3
> 
> ## d is a ** 3 ** column data frame
> 
> Now what I wish to do is programmatically convert d to a 4 column
> frame with names c("a","b","x","y"). Of course:
> 
> 1. The column classes/modes must be preserved (character going to
> factor and numeric remaining numeric).
> 
> 2. I assume that I do not know a priori which of d's
> components/columns are matrices and which are vectors.
> 
> 3. There may be many more columns which are vectors or matrix than
> just the three in this little example.
> 
> I can easily and sensibly accomplish these 3 tasks, but the problem is
> that I run afoul of data frame column naming procedures in doing so,
> about which the data.frame Help page says rather enigmatically:
> 
> "How the names of the data frame are created is complex, and the rest
> of this paragraph is only the basic story." Indeed!
> (This, of course, is shorthand for "Go look at the source if you want
> to know!" )
> 
> Anyway, AFAICT from the Help, any "simple" approach to conversion
> using data.frame results in "c.x" and "c.y" for the names of the last
> two columns. I **can** get what I want by explicitly constructing the
> vector of names via the following ugly hack; my question is, can it be
> improved?
> 
>> dd <- do.call(data.frame,d)
> 
>> dd
>   a b c.x c.y
> 1 1 4   a   d
> 2 2 5   b   e
> 3 3 6   c   f
> 
>> ncol(dd)
> [1] 4
> 
>> cnames <- sapply(d,colnames)
>> cnames
> $a
> NULL
> 
> $b
> NULL
> 
> $c
> [1] "x" "y"
> 
> 
>>  names(dd) <-  unlist(ifelse(sapply(cnames,is.null),names(d),cnames))
>   ##Yuck!
> 
>> dd
>   a b x y
> 1 1 4 a d
> 2 2 5 b e
> 3 3 6 c f
> 
> Cheers to all,
> Bert
> 
> 


-- 
Eik Vettorazzi

Department of Medical Biometry and Epidemiology
University Medical Center Hamburg-Eppendorf

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