[R] trouble converting an array to a dataframe

[Christopher W. Ryan]

I start with a dataframe called xrays. It contains scores on films from
each of two radiologists. It is in "long" format. I used the reshape
package to melt a data frame and then cast it into "wide" format, one
line for each patient (identified by redlognumb) with scores from both
radiologists for a given patient on the same line.

I named the result of the casting xrays.data. It is an array. I'd like
it to be a three-variable dataframe, with one column for scores from
each of two radiologists, and one column for redlognumb (because I will
then need to merge it with another dataframe that has a column named
redlognumb.) As you can see below, the data.frame() function turns
xrays.data into a two-variable dataframe. How can I get three columns
(or variables) into my final dataframe?

Thanks.


> head(xrays)
  redlognumb radiologis barrtotal
1          3          2        13
2          4          2        16
3          5          2        10
4          6          2        11
5          9          2        NA
6         10          2        NA

>melted.xrays <- melt(xrays, id=c("redlognumb","radiologis"))
>
> head(melted.xrays <- na.omit(melt(xrays,
id=c("redlognumb","radiologis"))))

  redlognumb radiologis  variable value
1          3          2 barrtotal    13
2          4          2 barrtotal    16
3          5          2 barrtotal    10
4          6          2 barrtotal    11
7          1          1 barrtotal    11
8          2          1 barrtotal     2
>

> cast(melted.xrays.2, redlognumb~radiologis~variable)

          radiologis
redlognumb  1  2
        1  11 NA
        2   2 NA
        3  12 13
        4  16 16
        5  12 10
       . .  . cut off for brevity . . .

> str(xrays.data)
 int [1:42, 1:2, 1] 11 2 12 16 12 13 18 8 19 14 ...
 - attr(*, "dimnames")=List of 3
  ..$ redlognumb: Named chr [1:42] "1" "2" "3" "4" ...
  .. ..- attr(*, "names")= chr [1:42] "1" "2" "3" "5" ...
  ..$ radiologis: Named chr [1:2] "1" "2"
  .. ..- attr(*, "names")= chr [1:2] "1" "80"
  ..$ variable  : Named chr "barrtotal"
  .. ..- attr(*, "names")= chr "1"
> data.frame(xrays.data)
   X1.barrtotal X2.barrtotal
1            11           NA
2             2           NA
3            12           13
4            16           16
5            12           10
6            13           11
7            18           NA
8             8           NA
. . . . cut off for brevity . . .


-- 
Christopher W. Ryan, MD
SUNY Upstate Medical University Clinical Campus at Binghamton
40 Arch Street, Johnson City, NY  13790
cryanatbinghamtondotedu
PGP public keys available at http://home.stny.rr.com/ryancw/

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