[R] An apply and rep question

[Liaw, Andy]

The trick is to rep() the index, not the data:

R> dat2 <- dat[rep(1:nrow(dat), each=2), ]
R> dat2
         DDate  OffP
1   2005-01-01 41.23
1.1 2005-01-01 41.23
2   2005-01-02 44.86
2.1 2005-01-02 44.86
3   2005-01-03 44.86
3.1 2005-01-03 44.86
4   2005-01-04 43.01
4.1 2005-01-04 43.01
5   2005-01-05 45.47
5.1 2005-01-05 45.47
6   2005-01-06 48.62
6.1 2005-01-06 48.62

Andy

From: Horace Tso
> 
> Hi list,
> 
> I'm sure the explanation must be laughably simple to the 
> experts out there, but I just could figure it out. I have a 
> simple data frame that looks like,
> 
> >head(da.off)
>        DDate  OffP
> 1 2005-01-01 41.23
> 2 2005-01-02 44.86
> 3 2005-01-03 44.86
> 4 2005-01-04 43.01
> 5 2005-01-05 45.47
> 6 2005-01-06 48.62
> 
> where the first column DDate currently is character, and OffP 
> is numeric. 
> 
> I want to duplicate every row 2 times, so I thought I use apply(),
> 
> x <- apply(da.off, 2, rep, each=2) 
> 
> The result is a matrix of all character,
> 
>  head(x)
>   DDate        OffP    
> 1 "2005-01-01" " 41.23"
> 1 "2005-01-01" " 41.23"
> 2 "2005-01-02" " 44.86"
> 2 "2005-01-02" " 44.86"
> 3 "2005-01-03" " 44.86"
> 3 "2005-01-03" " 44.86"
> 
> To convert it back to numeric, I did
> 
> x <- as.data.frame(x)
> x$OffP <- as.numeric(x$OffP)
> 
> However, the OffP column didn't convert correctly, a mystery 
> since they "look" quite alright above. (I know, I know, there 
> seems to be a space there. But why?)
> 
> head(x)
>          DDate OffP
> 1   2005-01-01  150
> 1.1 2005-01-01  150
> 2   2005-01-02  202
> 2.1 2005-01-02  202
> 3   2005-01-03  202
> 3.1 2005-01-03  202
> 
> Is this the wrong way to use apply or rep? 
> 
> Horace
> 
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