[R] reshaping column items into rows per unique ID

[Bert Gunter]

I believe you need to spend time with an R tutorial or two: a data frame
(presumably the "table" data structure you describe) can *not* contain
"blanks" -- all columns must be the same length, which means NA's are
filled in as needed.

Also, 8e^5 * 7e^4 = 5.6e^10, which almost certainly will not fit into any
local version of R (maybe it would in some server version -- others more
knowledgeable should comment on this).

Cheers,
Bert



Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Sun, Feb 25, 2018 at 4:59 AM, Allaisone 1 <allaisone1 at hotmail.com> wrote:

> Hi All
>
> I have a datafram which looks like this :
>
> CustomerID    DietType
> 1                           a
> 1                            c
> 1                            b
> 2                            f
> 2                             a
> 3                             j
> 4                             c
> 4                             c
> 4                              f
>
> And I would like to reshape this so I can see the list of DietTypes per
> customer in rows instead of columns like this :
>
> > MyDf
> CustomerID      DietType   DietType  DietType
> 1                                a            c               b
> 2                                 f             a
> 3                                 j
> 4                                 c              c             f
>
> I tried many times using melt(),spread (),and dcast () functions but was
> not able to produce the desired table. The best attempt was by typing :
>
> # 1) Adding new column with unique values:
> MyDf $newcol <- c (1:9)
> #2) then :
> NewDf <- dcast (MyDf,CustomerID~newcol,value.var=DietType)
>
> This produces the desired table but with many NA values like this :
>
> CustomerID    1   2   3    4     5    6     7   8   9
> 1                    a  c    b   NA NA NA NA NA NA
> 2                  NA NA NA  f     a  NA NA NA NA
> 3                  NA NA NA NA NA  j   NA NA NA
> 4                  NA NA NA NA NA NA c     c     f
>
>   As you see, the lette/s indicating DietType move to the right side each
> time we move down leaving many NA values and as my original files is very
> large, I expect that the final output would contain around 800,000 columns
> and 70,000 rows. This is why my code works with small data but does not
> work with my large file because of memory issue even though I'm using large
> PC.
>
> What changes I need to do with my code to produce the desired table where
> the list of DietTypes are grouped in rows exactly like the second table
> shown abover?
>
> Regards
> Allaisnoe
>
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>
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