Hi,

Take a look at this:

> identical(a,b)
[1] FALSE
> all.equal(a,b)
[1] "Attributes: < Component 2: 4 string mismatches >"
> rownames(a) <- rownames(b) <- NULL
> identical(a,b)
[1] TRUE
> all.equal(a,b)
[1] TRUE

HTH,
Jorge


On Mon, Aug 16, 2010 at 5:47 PM, array chip <> wrote:

> Hi, I am really puzzled by this. hope someone can help me
>
> I have a 2 small data frames "a" and "b" derived from a larger data frames.
> They
> look exactly the same to me, but identical() always returns FALSE.
>
> > a
>         a b
> 2 10011048 L
> 4 10011048 R
> 6 10011049 L
> 8 10011049 R
> > b
>         a b
> 1 10011048 L
> 3 10011048 R
> 5 10011049 L
> 7 10011049 R
>
> > identical(a,b)
> [1] FALSE
>
> some information about the attributes of the 2 data frames:
>
> > class(a)
> [1] "data.frame"
> > class(b)
> [1] "data.frame"
> > class(a$a)
> [1] "integer"
> > class(a$b)
> [1] "character"
> > class(b$a)
> [1] "integer"
> > class(b$b)
> [1] "character"
>
>
> However, if I generate these 2 data frame from scratches, identical() would
> returns TRUE
>
>
> >x<-as.data.frame(cbind(a=c(10011048,10011048,10011049,10011049),b=c('L','R','L','R')))
> >)
>
> >y<-as.data.frame(cbind(a=c(10011048,10011048,10011049,10011049),b=c('L','R','L','R')))
> >)
>
> > identical(x,y)
> [1] TRUE
>
> Looks like a & b objects takes some invisible residual information from the
> larger data frame where they were derived, which is not the same between
> them.
> But what is it?
>
> Thanks
>
> John
>
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>

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