[R] map column name in matrix to multiple elements

[Sarah Goslee]

Using dput() to provide your data is enormously easier.

Assuming the original column names of your data frame correspond to
the ColMap column of the second data frame, it's very straightforward:


mat <- structure(list(A = c(0.01, -2, -4), B = c(0.2, 1.4, -3), C = c(-0.3,
2.3, -2), D = c(0.8, 3.1, 0.4), E = c(-1, -2, 2.1)), .Names = c("A",
"B", "C", "D", "E"), class = "data.frame", row.names = c("S1",
"S2", "S3"))


matnames <- structure(list(ColMap = c("A", "A", "A", "B", "B", "B", "C"),
    element = c("Apple", "Arcade", "Almira", "Boy", "Balloon",
    "Bat", "Cat")), .Names = c("ColMap", "element"), class =
"data.frame", row.names = c(NA, -7L))

mat <- mat[, matnames$ColMap]
colnames(mat) <- matnames$element



R> mat
   Apple Arcade Almira  Boy Balloon  Bat  Cat
S1  0.01   0.01   0.01  0.2     0.2  0.2 -0.3
S2 -2.00  -2.00  -2.00  1.4     1.4  1.4  2.3
S3 -4.00  -4.00  -4.00 -3.0    -3.0 -3.0 -2.0


Sarah

On Fri, Aug 8, 2014 at 9:04 AM, Adrian Johnson
<oriolebaltimore at gmail.com> wrote:
> Hi:
> I am requesting help on matrix mapping.
>
> I have a matrix that is 5000 rows x 3000 columns in R env.
>
> Matrix:
>
>            A          B        C       D      E
>
> S1       0.01     0.2      -0.3     0.8    -1
>
> S2       -2        1.4       2.3      3.1    -2
>
> S3       -4         -3        -2        0.4    2.1
>
>
>
> I have another excel sheet, which when I import will have two columns..
>
>
> ColMap        element
>
> A             Apple
> A             Arcade
> A             Almira
> B             Boy
> B             Balloon
> B             Bat
> C             Cat
> .....
>
>
> I want to create another matrix with elements as column names and map
>  ColMap values onto elements.
>
>
>
> new matrix:
>
>                Apple      Arcade       Almira    Boy   Ballon ....
> S1              0.01     0.01            0.01     0.2       0.2
> S2              -2         -2                -2         1.4     1.4....
> S3              -4         -4                -4          -3      -3  ..
>
>
> I have no idea how I could do this in R.  would any one help please.
>
> Thanks
>

-- 
Sarah Goslee
http://www.functionaldiversity.org