[R] list to dataframe conversion-testing for identical

[Rui Barradas]

Hello,

But

 > all.equal(dat1,dat2)
[1] TRUE

So I guess it does have to do with floating-point equality, all.equal 
uses .Machine$double.eps. (Which could return FALSE on ocasions we would 
expect TRUE, when, for instance, the tolerance could/should be 
.Machine$double.eps^0.5.)

Rui Barradas

Em 01-07-2012 18:55, arun escreveu:
> HI R help,
>
> I was trying to get identical data frame from a list using two methods.
>
> #Suppose my list is:
> listdat1<-list(rnorm(10,20),rep(LETTERS[1:2],5),rep(1:5,2))
> #Creating dataframe using cbind
>
> dat1<-data.frame(do.call("cbind",listdat1))
> colnames(dat1)<-c("Var1","Var2","Var3")
> #Second dataframe conversion
>
> dat2<-data.frame(Var1=listdat1[[1]],Var2=listdat1[[2]],Var3=listdat1[[3]])
>
> #Structure is different in two datasets
>   >str(dat1)
> 'data.frame':    10 obs. of  3 variables:
>   $ Var1: Factor w/ 10 levels "18.6153321029756",..: 5 2 6 8 7 9 1 4 3 10
>   $ Var2: Factor w/ 2 levels "A","B": 1 2 1 2 1 2 1 2 1 2
>   $ Var3: Factor w/ 5 levels "1","2","3","4",..: 1 2 3 4 5 1 2 3 4 5
>> str(dat2)
> 'data.frame':    10 obs. of  3 variables:
>   $ Var1: num  20.3 19.2 20.5 20.9 20.5 ...
>   $ Var2: Factor w/ 2 levels "A","B": 1 2 1 2 1 2 1 2 1 2
>   $ Var3: int  1 2 3 4 5 1 2 3 4 5
>
> #Converting structure of dat1 to match da2 structure
> dat1<-within(dat1,{Var1<-as.numeric(as.character(Var1))
>      Var3<-as.integer(Var3)})
>
> head(dat1)
>        Var1 Var2 Var3
> 1 20.27193    A    1
> 2 19.17586    B    2
> 3 20.53197    A    3
> 4 20.93615    B    4
> 5 20.53498    A    5
> 6 21.02044    B    1
>> head(dat2)
>        Var1 Var2 Var3
> 1 20.27193    A    1
> 2 19.17586    B    2
> 3 20.53197    A    3
> 4 20.93615    B    4
> 5 20.53498    A    5
> 6 21.02044    B    1
>
>
> #New structure identical(str(dat1),str(dat2))
> 'data.frame':    10 obs. of  3 variables:
>   $ Var1: num  19.9 19 21.2 20.7 20.4 ...
>   $ Var2: Factor w/ 2 levels "A","B": 1 2 1 2 1 2 1 2 1 2
>   $ Var3: int  1 2 3 4 5 1 2 3 4 5
> 'data.frame':    10 obs. of  3 variables:
>   $ Var1: num  19.9 19 21.2 20.7 20.4 ...
>   $ Var2: Factor w/ 2 levels "A","B": 1 2 1 2 1 2 1 2 1 2
>   $ Var3: int  1 2 3 4 5 1 2 3 4 5
> [1] TRUE
>
>
>
> #structure is identical and dataframe looks to be same, but it is not identical.
>> identical(dat1,dat2)
> [1] FALSE
>
>
> Is it something to do with the floating point?
>
> Thanks,
>
> A.K.
>
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